its not how much boost is is how much knock your engine can handle (b4 it gives up) or your drivetrain raises the white flag
Get a good, solid and safe tune like from the gentleman above here and it should not be an issue. It has more to do with the tune and the quality of the gas (IE don't use crap 92 gas or anything like that). I have been running 19-20 tapering to 15 at redline for a while with no engine issues.