My compression on my stock motor was lowered via bowl work on the heads and different head gasket to 8.25:1. My new motor will be about 8.90:1 because of much better parts and the use of 116 fuel when I use the high boost setting. More compression makes the motor less boost dependant but of course reduces any room for f-ups via detonation , etc.. I could push mine up to a little over 9:1 but it would make zero room for errors.

Now 11+ : 1 no f'ing way !