Yeah but don't forget how much dough the FAST guys are dropping into having stock manifolds ported, or exrude honed or whatever they call it. The 6 pack intake is a good one for making HP, and you can put down some nice #'s with stock HP manifolds. With a stock 4bbl intake, not so much. Can still make some power, but it is way more restrictive than a 6-pack intake, which flow and performance wise keeps up with the modern street/strip intakes. With the right cam selection you can do a lot with the stock HP manifolds, but you would still gain more if changing to headers.