I'm actually starting to put very little stock in flow numbers these days. But flow observed on my SF-1020 was 263 cfm @ .500" with 267 cfm @ .600" and up. The exhausts always move 179-180 cfm with a pipe, and I say always because I don't do much with them. Oh and that was a 2.07" cut down to a 2.05 with a 1.6" exhaust. What is really important is what they act like @ 50"s of depression. J.Rob
