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GrimmSpeed Unequal Length Header – 08-14 WRX / 04-21 STI

GrimmSpeed Unequal Length Header – 08-14 WRX / 04-21 STI


The GrimmSpeed Unequal Length EJ Header utilizes single piece, mandrel bent runners to minimize disturbances to the exhaust gas along with an extremely durable cast 304 stainless steel collector to achieve keep each back of runners truly equal length which would be difficult to accomplish with a 4-into-1 welded collector. The low angle merge this collector makes for faster spool and unbeatable off-boost throttle response. To match this flow, the collector features machined internal diameters to perfectly match the 1 ¾” primary runners and 2” secondary pipe, eliminating unwanted “steps” in the exhaust flow.


In stock



Classic Subaru Sound with Unparalleled Performance

Over the years, GrimmSpeed Engineers have proven that we are capable of manufacturing the highest quality, best performing exhaust components for the Subaru aftermarket. While we might not always be the first to release a certain product, our major advantage is that we can take our time in testing and development, putting the product through countless hours and thousands of miles of testing. This ultimately ensures that once a component is in your hands, it will be the most-refined version of that product available. The all new GrimmSpeed Unequal Length EJ Header is a perfect example of this.

Our Unequal Length Header for the EJ-Series engines is very much the same. There are countless options out on the market for high-performing equal length header, but if you want to keep that classic Subaru rumble, there aren’t many great options.

The OEM EJ header really hasn’t changed much in the past 20+ years and it shows. The tight geometry and long cross-pipe between the two collectors are not optimized for flow or power. While the smaller diameter and volume may be good for low-end spool, the factory header gets choked out higher in the rev range. Simultaneously, it’s known that swapping to a more-equal length manifold with larger diameter runners offers additional performance potential. We set out to create a header that would be the best of both worlds, offering great performance and the unique sound that makes your car unmistakably a Subaru!

Quick Specs

  • Innovative 1.5 to 1 Unequal Length Runners – Each bank of runners is equal length, allowing for equal length performance with an unequal length sound
  • 4-into-1 Low-Angle Merge Cast Collector – Ensure minimal restriction and maximum performance
  • Smooth, Restriction-Free Flow Throughout – Single piece mandrel bent tubing welded to a single piece merge collector removes unwanted “steps”
  • Substantial Power/Torque Gains – +25hp and +25ft/lbs of torque over stock
  • Quickest Spooling Aftermarket Header – Faster spool and more power compared to the competition
  • No Tune Required – Safe to run, just bolt on
  • Gaskets and Hardware Included – Everything you need to get installed and on the road
  • Designed To Fit With Aftermarket Oil Pans – Fits with the STI oil pan or popular aftermarket options
  • Full 304 Stainless Steel Construction – 1/2″ flanges and 14ga runners for extreme durability
  • Manufactured and Welded In The USA – For consistency and top quality control
  • No Ground Clearance Loss – Clears factory skid plate without using spacers

  • J-Pipe/Turbo Bracket Included – Retain the support that other aftermarket header lose

  • Gaskets and Hardware Included – Everything you need to get installed and on the road

  • Manufactured and Welded In The USA – For consistency and top quality control


Additional Information

Weight 24.1 lbs
Dimensions 29.4 × 19.6 × 10.3 in


  • 2008-2014 WRX
  • 2004-2021 STI
  • 2002-2005 WRX 5MT (Requires STI Oil Pan and Pickup)
  • 2006-2007 WRX (Requires STI Oil Cooler and Feed Pipe)
  • 2004-2008 FXT* (Requires STI Oil Pan, Pickup, and Oil Cooler)
  • 2009-2013 Subaru Forester XT*
  • 2005-2009 Subaru Legacy GT*
  • 2005-2009 Subaru Outback XT*

*Unconfirmed, may require further modification


Installation Guide

Install Video Guide