Word to the guys who insist you HAVE to have 2" Primary headers and dual 3" exhausts

One Major 'trick' to running manifolds is you pretty much have to isolate the intake and exhaust events as much as possible (often by both reducing overlap and a late opening intake....i.e., very similar to an injected motor), so in a larger sense you intentionally lose/forfeit the overlap 'scavenging effect' so now you really have to make that intake runner work hard and breathe deep 'on its own'. The Exhaust really HAS to go out of the cylinder regardless and a restrictive manifold certainly adds resistence to the crank and to the opposing power stroke, but the high compression offsets that some as well by increasing the exhaust pressure and velocity.