Killer B Equal Length 4-1 Performance Holy Header 2-Bolt- Fits Subaru WRX 2002-2014 - STI 2004-2019 - MoreThe Killer B Motorsport Holy Header was developed using state of the art CAD software & simulations to determine the optimal design to increase power as much as possible throughout the rev range. Primaries were made as short as possible along with a single secondary which significantly decrease header volume allowing exhaust gas pressure to build quickly. The symmetrical 4 1 design maintains high and consistent exhaust velocity as RPMs rise. You can