My point was that higher CFM isn't a reliable indicator of superior boosted flow. The infamous 2JZ-GTE Supra factory twin turbo head needs no mods, not even a valve job, to produce 700 hp from 183" on high boost. The extremely similar (by flow and mean cross-sectional area) RB26, 7M, etc. are down by hundreds of hp under the same conditions.
Why is the GTE head so superior? Toyota doesn't know, the port locations were compromised to allow larger water jackets (the N/A GE head has better ports, but only NA). It was an accident.
When I was working in Japan, I saw tons of 2JZ cars tuned along with tons of RB26 cars, many running the same single turbo kits, and there never was "hundreds" of horsepower between those engines when running similar setups..,The 2JZ and the RB26 almost have identical power curves, its just shifted downward in the RPM band because of the added stroke, the 2JZ just acts like an RB with a stroker crank. There are lots of bone stock RB26's over 700rwhp running around Japan, the guy I worked with over there had an RB26 Stagea wagon with a HKS T51r, 750rwhp on an unopened N1 Rb26 motor..
