Cheers wasa, but I'm talking about outright performance...say you have an ECU capable of retaining VVT (or deleting it), and say the bottom end is fully forged...

I have heard the door will close on the blacktop head at around 550hp (after speaking to Ric Woods at CNC heads)...does this mean that's when its time to switch over to the ST170 head?...or even at lower boost pressures, will the ST170 head always flow more (hence more power) at the same boost pressure at a blacktop head