I think the only way to get more boost is to have a larger crank pulley made. The one on the supercharger is already small and if you make it smaller you run a risk of belt slipping. no one really knows how much boost you can get out of these engines with out blowing it. So you run a risk upping the psi. i would say on stock internals you wouldn't want to go any higher then 9-10psi and with that you are probably really close to what the engine can take.