E4-Series Equal Length Header


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WARNING: This product can expose you to chemicals which are known to the State of California to cause cancer and birth defects or other reproductive harm. For more information go to www.P65Warnings.ca.gov

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Create a smooth sounding exhaust note while increasing horsepower and torque with the PERRIN E4-Series Equal Length Header

Completely Redesigned - What's new

The new PERRIN E4-Series Equal Length Header comes with collectors that have been designed for better exhaust flow while allowing the headers to be constructed much more accurately. The improved exhaust flow and more precise construction increases power and reliability. The new E4-Series also has a low-profile design, allowing for excellent of ground clearance.

Equal Length Design

The equal length design of the PERRIN E4-Series Header produces smooth, balanced exhaust flow from the heads to the turbocharger giving you the best of two worlds: quicker turbo response as well as more horsepower and torque throughout the entire RPM band. While designed to fit to the factory up-pipe, our header will also mate with an aftermarket up-pipe that fits factory header and turbo, as well as any rotated turbo kits compatible with the factory header.

Perfectly sized for more HP

You won't see grossly over-sized tubing to make our header "look" impressive, this just slows exhaust gas flow and reduces response. This header uses 1.5" primary tubing that is expanded at the flange to fit the Subaru exhaust port size. This size tubing is perfectly designed for cars up to about 400 wheel horsepower. You can see from our dyno graphs that there is a significant gain in horsepower and torque across the entire RPM band compared to an OEM Subaru header. For those looking to go beyond 400 wheel horsepower, check out our E4-Series Big-Tube Equal Length Header.

Flanges & Port Matching

PERRIN Flanges are CNC machined from 304 stainless steel and counterbored on the back side to make smoother transitions. Flange ports are sized properly to ensure exhaust coming out of the head has a smooth, unobstructed path to the tubes. The ports are not over-ported which would cause gaskets to burn out quickly. The tubes are expanded inside the flanges for a perfect fit and smooth flow of exhaust gases to the tubes.


Due to its equal length design, the PERRIN Header will alter the tone of your exhaust. The exhaust pulses from the engine are equalized and spread out producing a smoother, more refined sound. A byproduct of the equalization is a significant reduction in the volume of your exhaust sound. Some describe the sound as being similar to an inline four cylinder engine exhaust.


PERRIN E4-Series Equal Length Headers feature a brushed stainless steel finish.

Oil Pan

Most headers collect on the passenger side of the engine, and due to space constraints, are not equal length and compromise exhaust flow. Because we use the added room provided by the oil pan (only on 2.5L turbo pans), we can create a smooth transition of the header primaries to the collectors, and collectors to up-pipe, providing more power and torque then the competition.

2.0L WRX engines will need the 2.5L STI oil pan install kit. Please shop our installation kits for more information.

5 Year Warranty

PERRIN Performance warrants to the original purchaser that all PERRIN products will be free from defects in material and workmanship within a sixty (60) month period from the date of purchase. *Some exclusions apply
» Read Full Warranty

Off Road Use Only

This product is legal in California only for racing vehicles which may never be used upon a highway. Check your local and federal laws prior to installation.
» Learn More

Warranty Exclusions

We will not warranty any exhaust part that fails or has warped flanges with header wrap installed. While header wrap protects the engine from heat as well as provides some performance benefits, it greatly reduces the life of any stainless steel part. Header wrap greatly increases the rate of corrosion (even stainless steel corrodes), added to that the actual temperature of the metal is much hotter, reducing its lifespan even further. Operation of vehicle without installation of splash guard will void warranty.

We will not warranty any flanges that are warped away from the weld if any aftermarket gaskets are used. Only OEM Subaru gaskets are to be used on this PERRIN Exhaust part, with the exception of downpipes for turbo kits. Subaru provides the proper crush gasket that still becomes flat when tightened (or over tightened) in comparison to aftermarket gaskets which can have a crush ring that is too thick, causing a hot-spot in the middle of the flange. These will warp the flanges of your PERRIN exhaust part, causing a permanent exhaust leak that will not be fixable with a new gasket.


Warranty Details

This product features a 5 year warranty Read Full Warranty

Tech Department




Weight 12 lbs.
Material 304 Stainless Steel

In The Box

In The Box

(1) PERRIN E4-Series Equal Length Header
(1) PERRIN License Plate Frame

Dyno Charts

Dyno Charts

Proven Horsepower

Dyno Chart

07 STI Stock Header vs. PERRIN Header

This dyno graph shows what one of our customers found after installing our equal length header on his STI. The turbo spools quicker, the engine make more torque and horsepower over the stock header. As long as you are ok with the smoother quieter sound from the header, you will love the additional 20WHP and 30ft-lbs more tq! This test was also done on NASIOC in public forum comparing all kind of headers to one another. The PERRIN Header came out on top!

Dyno Chart

2.0L Stage 2 WRX vs. Equal Length Header

This test was done on our shop 02 WRX (aka Project 15K), and you can see that even on the 2.0L engine, the PERRIN Header is worth 10WHP and 15ft-lbs of tq. This test was done back to back in roughly 20minutes of work, so you can see the gains are very real.

Dyno Chart

GT3582R w/.82ar vs. Equal Length Header

This graph shows a customer of ours that had one of our rotated turbo kits installed with a GT3582R. Even on these larger turbos the PERRIN Equal Length Header also shows the same gains. The turbo spools quicker allowing the engine to make more torque (20-50ft-lbs) and in turn make more Wheel HP (10-15WHP).

Dyno Chart

GT3582R w/Equal Length Header Boost Curve

This is the boost curve of the same above car. You can see how much quicker the turbo spools up. The PERRIN Header reduces turbo spool time anywhere from 100-250RPM, making the car even more drivable.

Dyno Chart

05 Legacy GT vs Equal Length Header

Here is another test done on a Legacy GT. This also represents the 08 WRX models as they have very similar turbos and engines. In this test, the header was installed after a Stage 2 tune was done on the car, then after the header was installed, additional tuning was done adding to the 30WHP and 40ft-lbs of torque.

Compatibility Notes


2002-2005 WRX Yes, requires oil pan with header cutout and oil pickup tube, and custom modification to the radiator line to the transmission.
2002-2005 WRX Automatic Transmission Yes, requires modifications to radiator.
2006-2007 WRX Yes, requires 2002-04 WRX oil cooler assembly and oil feed pipe.
2004-2008 Forester XT Yes, requires oil pan with header cutout, oil pickup tube, 2002-04 WRX oil cooler assembly, and 2002-04 WRX oil feed pipe.
2009-2013 Forester XT Yes, no modification required
2004-2007 STI Yes, no modification required
2005-2009 Legacy GT Yes, no modification
2008-2014 WRX Yes, no modification
2015-2018 WRX No
2008-2014 STI Yes, no modification
2015-2018 STI Yes, no modification
CSF Radiator with Built-in Oil Cooler No

See our install kits here.

*OEM parts

Oil Pan with Header Cutout Subaru Part #11109aa151 - Est. Price $108.28
Oil Pick Up Tube Subaru Part #15049aa110 - Est. Price $26.98
Oil Cooler Assembly Subaru Part #21311aa051 - Est. Price $219.95
Oil Feed Pipe Subaru Part #21317aa02 - Est. Price $43.38
O-ring (not needed unless damaged) Subaru Part #21370ka00 - Est. Price $5.82

The PERRIN Performance Header is not compatible with header wrap material. Using Header wrap will void all warranties. The PERRIN Performance header will not fit Moroso 20965 oil pans. Please call with further questions.



Keep in mind, these tests are ONLY for comparison purposes to help provide an answer to the question "How loud is this?" These tests are not claiming that any of these systems will pass any local law pertaining to a decibel limit for your car. If you are unsure of a system passing a local decibel limit law, please have a professional test your exhaust to determine if it’s legal.


Shipping Information

  • Item Requires Shipping
  • 19.0 lbs.
  • W9.0000” x H14.0000” x L27.0000”
  • This item ships in its own box.