ok, after much thought and irritation i have decided to rebuild a GSR block. Now i'm trying to figure out why on a turbo build one would use a lower compression piston. Say 12.5:1 N/A as compared to 9.1:1 turbo. My thinking was the higher compression one would need less boost to produce more prower, where as with a lower compression one would need more boost to produce the same power. Mind you this block will be sleeved with a deck support & with 84mm pistons.