more fuel pressure = more fuel injected by the injector at the same duty cycle.
injectors, ECU, MAFS, etc should all be able to handle about 12-13 psi (need an upgraded intercooler!!). i'm running 11.5 with an S-AFC (dyno tuned with a wideband O2 for correct A/F ratio) and everything works fine (although boost falls from 6000rpm to 9si at redline... just a characteristic of that tiny-*** turbo
). if in doubt, get on a dyno with a wideband and see what your A/F ratio is.
P.S. I'm assuming you're talking S13 SR (T25, 370cc/min injectors). on an S14 SR you have a better turbo (T28) that can run more boost safely and bigger injectors (440cc/min), dunno about the MAFS...