GrimmSpeed Unequal Length Header 2008-2014 Subaru WRX / 2004-2021 Subaru STI

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Product details

This is the all new GrimmSpeed Unequal Length EJ Header. 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 GrimmSpeed Header out spooled the competition’s equal length header by 50rpm while making similar boost levels. Our Header produces more torque than the equal length manifold right out of the gate, producing about 15ftlbs more throughout spool up. At peak, the GrimmSpeed Header was able to produce and extra 2 ft/lbs of torque and an additional 21 hp compared to the equal length setup.

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


  • 04-21 Subaru STI
  • 08-14 Subaru WRX
  • 09-13 Subaru Forester XT*
  • 05-09 Subaru Legacy GT*
  • 05-09 Subaru Outback XT*
  • 02-05 Subaru WRX 5MT (Requires STI Oil Pan and Pickup)
  • 06-07 Subaru WRX (Requires STI Oil Cooler and Feed Pipe)
  • 04-08 Subaru Forester XT* (Requires STI Oil Pan, Pickup, and Oil Cooler)
  • 04-06 Subaru Baja XT* (Requires STI Oil Pan, Pickup, and Oil Cooler)

*Unconfirmed, may require further modification