13 psi could be to much but it depends what fuel your using and the over all condition of your engine. It may well be fine but the only way to find out for sure is to have it dyno tuned cause on the road not all detonation is audible. My S13 CA18DET is more than happy to run 12-14 psi all day long with similar mods and running on optimax I have checked it on the nissan consult machine and there was absolutly no detonation or pining so its possible 13 psi is fine but have it checked. If you don't want to have it dynoed put a tank of premium in it and take it high up in the rev range in a low gear. (6000-7000RPM) if you can hear even a small rattle coming from the engine get the boost lowered! This is not the correct method but rather a quick alternative the forman at work taught me