That's exactly what I'm saying. More air doesn't always equal more power, unless you have a way out of whack combination like a 200cfm head on a 500 inch stroker. To answer your question I think the exhaust has a lot to do with it but I really don't know the answer other than I think a strong exhaust port helps an engine stay in "tune" longer so that it hangs on in power after peak. I also think cam events become more critical and header design becomes a bigger player with a good exhaust port. I've had W9's flow 260cfm through a 1.6" valve that fell far short of the 2.06 cfm/hp on the intake side. I've also had engines that flowed terrible on the exhaust perform stunningly well. I really don't know the answer to your question but I would revert to the reputation of whatever cylinder head you have in mind for the answer. J.Rob
