If your load tables are off in the pcm, the gauge will be off as well.Mine is off by 2-3 PSI, but it'll peg at like 10-ish for me.
yeah i have a custom tune. but still dont know how much boost i am making.I put one in for looks. Honestly a boost gauge is useless once your car is tuned. My needle goes into the boost zone for show and tell and that is enough for me. Really easy install by the way.