how much boost did a stock 1.8 turbo sunbird run

around 7-9 psi depending on gear, outside pressure, and a few other variables. Same thing as a turbo 2.0.

thanks so how could the 1.8 turbo run 7-9 psi on cast pistons. and could the 2.0 na run 7-9 psi on cast pistons

you can boost with cast pistons, but tuning has to be dead on. detonation is what kills pistons, but if you have your tuning right, you wont have detonation. forged pistons are stronger and can stand some detonation, but if tuning is to far off, you can still kill foged pistons.

i wouldnt boost an N/A 1.8 or 2.0l. the turbo motors havea lot lower compression (8.0 compared to 9.0 or higher on the n/a), again to reduce the chance of detonation.