i would say your boost gauge maybe out mate, mine is 2 psi lower than the car boosts, u need a nomad or something as good to try and get a decent reading.

i had the problem when mine was standard, kept cutting out on boost, thought it was a misfire, changed everything, my boost gauge said 8 psi, i thought it was correct, turned out i was hitting the boost limit, as i used a nomad gauge and it was hitting nearly 11psi!!