GrimmSpeed Unequal Length EJ Series Exhaust Manifold 2008-2014 WRX / 2004-2021 STI

GrimmSpeed proprietary Unequal Length Header design features an innovative runner layout that delivers the iconic Subaru rumble without sacrificing the performance benefits of equal-length engineering. Each bank of runners is equal in length to itself, but one bank is 1.5× longer than the other—allowing for a deep, classic boxer sound while maintaining exceptional exhaust tuning and flow.

To ensure smooth, uninterrupted exhaust travel, we use single-piece, mandrel-bent runners, paired with an extremely durable cast 304 stainless steel collector. This cast collector enables true equal-length pairing within each bank—something nearly impossible to achieve with a traditional welded 4-into-1 collector. Its low-angle merge improves turbo spool and delivers outstanding off-boost throttle response. The internal diameters are precision-machined to match our 1.75" primary runners and 2" secondary pipe, eliminating steps and turbulence inside the collector.

As with all GrimmSpeed exhaust components, the header is built for durability and thermal efficiency. 1/2" thick flanges on both head and up-pipe sides pair with 14-gauge stainless runners for excellent strength and heat retention.

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 - Ensures 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 for installation to get 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 14 gauge runners for extreme durability
• Manufactured and Welded In The USA – For consistency and top quality control

FITMENT:

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

*Unconfirmed, may require further modification