For a gsr motor that is going to run on 93 octane I wouldn't run a stock motor past 300whp. On race gas big numbers are possible but you are one bit of detonation away from losing it.
+1....detonation is the enemy of everything. boost is just another way to make it happen if its not tuned rite. race gas will eliminate it, but i dnt think ud wanna run race gas regularly on the street.