I think that going even to 6 PSI is going to call for lower compression or more than 92 octane. My next guess is that the cams are a long way from optimum for a turbo. I would think that 3 or 4 PSI would get you back to just below sea level where 92 would still work. You'd have to stay away from the lowlands... or be willing not to step on it. With Reg. Unleaded motors you can lean on them more because you have a lot less compression to start with. For what it would take to do it right, you could probably buy a used Kompressor. Good luck.