The 4-2-1 or 6-2-1 ARK R-spec header is a highly designed Racing spec Header. It’s designed to get the most out of high revving race tuned motors. It includes TIG welded connections, de-burred & ported inlets/outlets, for better flow, larger piping and a CNC mandrel with bent primaries. The primaries exit into a special laser guided-designed merge equal collector which allows smooth exhaust flow, ideal for racing applications. Has increased dyno proven horsepower and torque from mid-range to redline and comes semi-brushed with mirror polished.