Before I decided to tear my crap down I had the wastegate actuator pulled off my e316g and saw 28psi sometimes creeping to 30psi. That was with 750's, Supra pump, and DSMLINK. The most CFM I think my motor ever saw was just under 30psi on my 20g on C16. I love to push for as much boost as I can, but it has caused some destruction on a few occasions. I guess I should pay attention to my knock sum a little better or at least not ignore it rofl.
I'm just now (picked up the motor yesterday) beginning a 6 bolt G4CS build, and am hoping to run some 1/2 decent boost on it. I'm actually going to be selling my 2G to finance the motor build and then sourcing a 1G AWD shell AFTER the motor is finished. That way I know I'll have as much $ (hopefully) as I need. With Eagle crank and built 8:5 internals/head it should do allright. The most boost I've ever witnessed was just under 80psi on a fully built Dodge Ram with a 12v Cummins in it. The guy had actually modified a compression tester to be his boost gauge!