Best Exhaust For Sti: Compare Cat-Back and Axle-Back Systems

#1 · Best Overall

1. Borla 140595 Cat-Back

• Compatible with Vehicle Type: Car
• Material: Stainless Steel
• Weight: 48 lb
• Installation Type: Bolt-On

Best for: No-drone cat-back shoppers.

Why it ranks #1: Listed for 2015–2021 WRX and WRX STI, this T-304 stainless cat-back has bolt-on installation, dual split rear exits, and a no-drone guarantee.

Borla’s no-drone guarantee is the clearest differentiator for this T-304 stainless cat-back, addressing buyers concerned about exhaust cabin resonance. Dual split rear exits and polished 3.5-inch tips on each side give the system a defined outlet layout, with fitment listed for 2015–2021 WRX and STI models.

The no-drone guarantee directly addresses resonance as a buying concern, while the dual split rear-exit configuration specifies how the system terminates at the back of the car. Polished 3.5-inch T-304 stainless tips on each side give the outlets a matched finish, and all-welded construction is another stated build detail. Bolt-on installation is listed, and the application covers 2015–2021 WRX and STI models with the specified engine range.

Skip it if you prefer a single exit; Tomei TB6090-SB02C lists a titanium single-exit muffler kit for specified WRX and STI applications.

This fits 2015–2021 WRX and STI owners seeking a bolt-on cat-back with a no-drone guarantee and dual split exits. Buyers should account for the dual-outlet layout and confirm their application matches the listed engine range.

Listed on Amazon as: BORLA 140595 Cat-Back Perf. Exhaust Sys. for 2015-2021 Subaru Impreza WRX & WRX STI 2.0L/ 2.5L 4 Cyl. T-304 SS S-TypeDual Split Rear Exit Dual 3.5" Round Polished T-304 Stainless Tips Each Side

#2 · Best Burnt-Tip Cat-Back

2. Invidia N1 Titanium Cat-Back

• Compatible with Vehicle Type: Car
• Material: Titanium
• Weight: 47 lb
• Installation Type: Bolt-On

Best for: Burnt-tip dual-outlet fans.

Why it ranks #2: Its listed fit covers 2015-up four-door WRX and STI, with 3-inch piping, 4-inch burnt titanium tips, and mandrel-bent stainless piping.

Twin 4-inch burnt titanium tips give this Invidia N1 cat-back its most visible distinction, while 3-inch mandrel-bent piping is specified to support exhaust flow and reduce back pressure. It is listed for 2015-up four-door WRX/STI models, pairing its rear styling with a defined application.

The 76 mm, or 3-inch, mandrel-bent stainless-steel piping is described as promoting exhaust flow and reducing back pressure, linking its diameter and bends to the stated operating purpose. Twin 101 mm, or 4-inch, single-layer burnt titanium tips create a dual-outlet appearance. CNC-machined flanges and bolt-on installation are also listed, giving buyers construction and installation details. Fitment is specified for 2015-up four-door Subaru WRX/STI models.

Skip it if you need a specified 2015–2021 application without the four-door limitation; Tomei TB6090-SB02C lists sedan and other named ranges.

This suits four-door 2015-up WRX/STI owners who want Invidia’s dual burnt-tip N1 layout and 3-inch piping. The stated body-style fitment is a boundary, so buyers should match their vehicle to that exact application.

Listed on Amazon as: Invidia (HS15STIGTT) N1 Titanium Burnt Tip Dual Cat-Back Exhaust System for Subaru WRX/STI

#3 · Best Quad-Tip Option

3. Invidia Gemini/R400 Cat-Back

• Compatible with Vehicle Type: Car
• Material: Stainless Steel
• Weight: 49.5 lb
• Installation Type: Bolt-On

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Best for: Power-focused cat-back buyers.

Why it ranks #3: The listing identifies a 2015-and-newer WRX/STI back exhaust with quad titanium tips, stainless construction, and bolt-on installation.

Invidia highlights a 4-inch stainless-steel bell mount as the feature intended to free excess gas, with its supplied dyno description reporting several horsepower units added over the stock exhaust. That makes this bolt-on system a choice for 2015-and-newer WRX and STI owners prioritizing the stated power potential.

The 4-inch stainless-steel bell mount is presented as a way to free excess gas, tying the system’s physical design to its power-focused purpose. Invidia also cites a dyno chart showing several horsepower units added over the stock exhaust, giving buyers a specific claimed outcome rather than only a styling detail. Its bolt-on installation type supports a direct-fit installation approach, and the listed application is 2015+ Subaru WRX/STI. Gaskets are included.

Skip it if you need a listed 2015–2021 application and quad polished tips; Borla 140595 specifies both.

This is for WRX/STI owners seeking Invidia’s stated power-oriented design and a bolt-on system. Its supplied description lists 2015+ fitment but does not provide an upper year limit, so that scope is the key fit consideration.

Listed on Amazon as: Invidia HS15STIGM4ST Exhaust System (Back Exhaust2015+ Subaru WRX/Sti Gemini/R400 Single Layer Quad Titanium Tip Cat)

#4 · Best Titanium Option

4. Tomei Full Titanium Muffler Kit

• Compatible with Vehicle Type: Car
• Material: Titanium
• Installation Type: Bolt-On

Best for: Titanium single-exit fans.

Why it ranks #4: This bolt-on titanium muffler kit lists compatibility with 2011–2021 STI EJ models and includes hardware for bolt-on installation.

Full titanium construction and a single-exit layout distinguish Tomei’s muffler kit, while included bolt-on hardware supports installation without sourcing the listed fasteners separately. Its stated applications span EJ-powered WRX and STI ranges as well as 2015–2021 WRX FA20DIT sedans, giving buyers specific fitment targets.

The titanium material is the central construction detail, and the single-exit format gives the rear layout a clear distinction from dual-outlet systems. Tomei includes all hardware for bolt-on installation, which can simplify gathering the components specified for mounting. Fitment lists 2008–2014 WRX EJ, 2011–2021 STI EJ, and 2015–2021 WRX FA20DIT sedan applications. Those engine and body details matter: the product is not presented as a universal WRX/STI fit.

Skip it if you need a dual-exit layout; Borla 140595 lists dual split rear exits and dual tips on each side.

This is for buyers whose listed WRX or STI engine and body match the application details and who prefer titanium with a single exit. Check those stated ranges carefully; the supplied fitment is specific rather than universal.

Listed on Amazon as: Tomei Full Titanium Muffler Kit Compatible with 2008-14 WRX EJ, 2011-21 STI EJ and 2015-21 WRX FA20DIT Sedan – Single Exit – TB6090-SB02C

#5

5. PHILTOP Cat-Back System

• Weight: 26.2 lb

Best for: Resonated cat-back seekers.

Why it ranks #5: This cat-back lists fitment for 2015–2017 WRX and WRX STI, making its stated generation range useful for owners of those model years.

Tuned resonators paired with low-restriction mufflers give this PHILTOP cat-back a stated approach to reducing noise while retaining a performance-exhaust layout. Its listed fitment is limited to 2015–2017 Subaru WRX and WRX STI, a useful boundary for owners choosing a full-system replacement.

This is a cat-back system, so it covers more than an axle-back, while its larger pipes, low-restriction mufflers, and tuned resonators are described as supporting noise reduction. Those components give buyers a specific sound-management rationale rather than relying on an unspecified exhaust note. The listing identifies stainless steel as the construction material and names 2015–2017 WRX/WRX STI as the compatible range. That narrower year span matters when choosing it for an installation.

Skip it if you have a 2018–2021 WRX STI; Borla 140595 lists fitment through 2021.

This suits 2015–2017 WRX and WRX STI owners wanting a cat-back with tuned resonators and low-restriction mufflers. Its listed year range is the main boundary; owners of later models should look at a system covering their year.

Listed on Amazon as: PHILTOP Cat-Back System Fit for 2015-2017 Subaru WRX/WRX STI

#6 · Best Axle-Back

6. Extreme Online Store Stainless Axle-Back

• Compatible with Vehicle Type: Fits ALL 2015-2021 Subaru WRX STi Models
• Material: Stainless Steel
• Weight: 8 lb

Best for: Complete axle-back kit shoppers.

Why it ranks #6: The listing covers all 2015–2021 WRX STI models and includes left and right exhaust sections, hangers, gaskets, and fasteners.

The included left-and-right hangers, gaskets, and nut-and-bolt pairs make this axle-back more of a supplied installation kit than a tips-only purchase. Its polished stainless-steel quad tips are listed for all 2015–2021 WRX STI models, giving buyers a clear application and a matched rear appearance.

The package includes a left-and-right axle-back assembly, two pairs of hangers, a pair of gaskets, and a pair of nut-and-bolt sets, so buyers have several listed mounting components together. Its polished stainless-steel construction pairs with double-wall quad tips for a coordinated rear finish. The listing specifies all 2015–2021 WRX STI models and says the product was test-fitted before shipment. This remains an axle-back replacement, not a listed full cat-back system.

Skip it if you want a full-system cat-back; Borla 140595 is listed as a cat-back for 2015–2021 WRX and STI.

This fits WRX STI owners wanting a polished quad-tip axle-back with mounting hardware and gaskets supplied together. Its stated application is 2015–2021 WRX STI models, and buyers seeking a full cat-back should choose a different system type.

Listed on Amazon as: Replacement For 2015-2021 Subaru WRX STi STAINLESS STEEL POLISHED SILVER Muffler Axle Back 4" Double Wall Quad Tips Exhaust

#7

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7. Generic Burn-Style Axle-Back

• Compatible with Vehicle Type: Car
• Material: Stainless Steel

Best for: Polished axle-back upgrade.

Why it ranks #7: This stainless axle-back fits 2015–2021 WRX and WRX STI and pairs 2.50-inch piping with 4-inch double-walled burn-finish tips.

The 4.0-inch double-walled tips give this stainless axle-back a pronounced finish while keeping the change focused at the rear of the exhaust. Its 2.50-inch piping and included mufflers and gaskets make it a defined option for 2015–2021 WRX and STI owners seeking a matching axle-back assembly.

This is an axle-back rather than a complete cat-back, so its scope is limited to the rear muffler section. The 2.50-inch piping provides the listed exhaust route, while the 4.0-inch double-walled tips add a larger visible outlet without changing the stated installation category. Stainless-steel construction and a polished burn finish give the assembly its specified material and appearance. Mufflers and gaskets are included, and fitment is listed for 2015–2021 WRX and WRX STI models.

Skip it if you need a full cat-back; Borla 140595 is listed as a cat-back system for 2015–2021 WRX and STI.

This suits 2015–2021 WRX and STI owners who want a stainless axle-back with prominent double-walled tips. Choose it for a rear-section change, not a complete cat-back replacement; the listed fitment covers those model years.

Listed on Amazon as: Generic Burn Style Stainless Axle Back Muffler Exhaust for Subaru WRX & STi 2015-2021, MF-SWRX15-BUR

#8

8. Extreme Online Store Resonated Midpipe

• Compatible with Vehicle Type: Fits ALL 2015-2021 Subaru WRX STi Models -…
• Material: Stainless Steel
• Weight: 20 lb
• Installation Type: Bolt-On

Best for: Factory-midpipe replacement buyers.

Why it ranks #8: Its 3-inch midpipe kit is listed for 2015–2021 WRX STI, but it does not work with aftermarket exhaust systems or the SPT midpipe.

A three-piece, 3-inch resonated mid-pipe kit gives this listing a narrower role than a full exhaust system. Its stainless-steel construction and included gaskets and hardware make it a focused replacement option for 2015–2021 WRX STI owners whose exhaust remains compatible with the stated setup.

This kit consists of a three-piece 3-inch mid-pipe tube, five gaskets, and a bag of hardware, so its contents center on the mid-pipe connection rather than a complete exhaust. The resonated design is part of the product description, while polished stainless steel specifies its material and finish. Fitment is listed for 2015–2021 WRX STI models, but the listing explicitly excludes aftermarket exhaust systems and the SPT mid-pipe. That compatibility limit is central to selecting it.

Skip it if you have an aftermarket exhaust or SPT mid-pipe; Borla 140595 is a listed complete cat-back alternative.

This is for 2015–2021 WRX STI owners replacing a compatible mid-pipe and wanting the listed 3-inch resonated kit. It is not compatible with aftermarket exhaust systems or the SPT mid-pipe, so that setup boundary is decisive.

Listed on Amazon as: Replacement For 2015-2021 Subaru WRX STi T304 STAINLESS STEEL POLISHED SILVER Resonated MidPipe Kit

#9

9. DNA Motoring CBE-WRX02-BT

• Compatible with Vehicle Type: Car
• Material: Stainless Steel
• Weight: 21 lb

Best for: Older WRX power-focused builds.

Why it ranks #9: This T-304 stainless cat-back fits 2002–2007 Impreza WRX and STI, so it suits an older STI rather than newer generations.

DNA Motoring cites a dyno-proven 15–25 horsepower increase and low-end torque gains for this stainless cat-back, giving older WRX/STI owners a specific performance claim to consider. Its stated fitment is 2002–2007 Subaru Impreza WRX and WRX STI, not the newer STI generation.

The T-304 stainless-steel construction, computerized mandrel bends, and TIG-welded CNC-machined flange are listed as durability-focused details, with the flange described as resisting pressure and corrosion. DNA Motoring also claims a dyno-proven 15–25 horsepower increase and low-end torque gains, alongside a deep, smooth tone and smooth exhaust-gas flow. Those claims make the system performance-oriented, but its application remains limited to 2002–2007 Impreza WRX/WRX STI models.

Skip it if you own a 2015–2021 WRX STI; Extreme Online Store EXT-MP011 lists that newer range for its mid-pipe kit.

This suits 2002–2007 Impreza WRX and WRX STI owners considering the stated performance claims and stainless construction. Its older-model application is a firm fit boundary, so it is not the choice for later STI generations.

Listed on Amazon as: DNA MOTORING CBE-WRX02-BT Stainless Steel Cat Back Exhaust System [Compatible with 02-07 Subaru Impreza WRX/WRX STI]

#10

10. Spec-D Tuning N1 Cat-Back

• Compatible with Vehicle Type: Car
• Weight: 25 lb

Best for: Older turbo WRX owners.

Why it ranks #10: Its listed fitment is limited to 2002–2007 Impreza WRX STI 2.0L and 2.5L turbo models, excluding the newer STI generations.

Its narrow application is the key differentiator: this stainless N1 cat-back is listed for 2002–2007 Subaru Impreza WRX and STI models with 2.0L or 2.5L engines, excluding non-turbo versions. That makes it an option for owners of the specified older turbo cars, not newer STIs.

The cat-back format replaces the exhaust section identified by its system type, while stainless-steel construction is specified in the product listing. Fitment is restricted to 2002–2007 Impreza WRX/STI models with 2.0L or 2.5L engines, and the listing expressly excludes non-turbocharged models. The seller describes installation as needing little to no modification at best, but that wording is not a guarantee of a modification-free fit. The 25-pound listed weight is also relevant when handling the assembly.

Skip it if you have a 2015–2021 STI; Borla 140595 lists that newer WRX/STI application range.

This is for owners of 2002–2007 Impreza WRX or STI turbo models with the listed 2.0L or 2.5L engines. The non-turbo exclusion and older year range are firm boundaries to weigh before choosing it.

Listed on Amazon as: Spec-D Tuning Stainless N1 Catback Exhaust System