depends on fuel, knock, detionation, timing and egts. I run 21-22psi but thats because i have return line, boomba rail, wideband etc. But this doesnt mean your car can do it. Get fuel and watch the afr and timing.
you need to be careful....get a scan gauge...then a widebnd....and then start fucking with that shit....the more boost you run with out a proper way to adjust it (i.e. a fuel conroller, do not buy a map clamp imo) will just transfer over to more problems....and the higher boost you run the more you need to watch the timing on the scan guage (so get W/M injection, that will help).....stock fuel- 17spike.....fpr mod- 20 (maybe more, depending on how you have it set) fpr/ W/M inject- 22 (and adjust accordingly with your AFC)...good luck