Killer B Motorsport 02-14 WRX / 04-21 STI 4-1 Holy Header Exhaust Manifold w/ V Band Up-Pipe | HH4-1

The 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. Short as possible primaries with a single secondary decrease header volume significantly, allowing exhaust gas pressure to quickly build. 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 that you will immediately notice in throttle/boost response and the ability to hold more power higher into the revs. Cast Collector. The collector is thick-walled cast 347 (321) stainless. The casting removes several welds, and each weld removed is one less flow disruption (reduced turbulence). The casting has features milled into it that assure the primary tubes fit VERY concentric every time. Using a casting allows the collector to be designed as a true high-velocity mer