Killer B Motorsport 4-1 Holy Header Exhaust Manifold DIY Rotated 2002-2014 WRX / 2004-2021 STI

The Killer B Motorsport Holy Header was developed using state of the art CAD software & simulations to determine optimal design to increase power in the mid to high RPM range. Short as possible primaries with a single secondary significantly decrease header volume allowing exhaust gas pressure to build quickly. Symmetrical 4-1 design maintains high and consistent exhaust velocity as RPMs rise. You can expect faster spool up time compared to long primary/double secondary designs. A difference you will immediately notice in throttle response and the ability to hold more power higher into the revs. This is a DIY kit, you will have to construct the uppipe to your needs! If you are looking for a direct replacement header please use Killer B's other header listings which can be found on our site. Features include: Short Equal Length Primaries. The shortest possible length primaries you can have on an Equal Length header. Short means less header volume and quick spool up. Symmetrical Pr