DOC Race manifolds are built in house by our highly trained and skilled fabricators who have years of experience. Our 6 cylinder manifolds have been known to make over 1200whp and are sold worldwide. Many manifolds have been sold to to racers across the country competing in NHRA and BOTI. We only use high quality 304 stainless steel tubing with thick wall to insure absolutely no cracking or warping even under high horsepower applications. We custom make our own collectors which over the years have been developed with lowest angle possible. This produces minimal exhaust turbulence which equals fast spool and high horsepower capabilities. All manifolds go through a major port and polish job to guarantee the absolute highest flow possible. Our porting process has been dyno proven over and over again to reduce lag as well as aid in peak power.