and my Z is doing the same thing. It goes to 14psi and then drops down to 10. I am changing out my mbc to a ebc and see if thats going to make a difference. Also when i had just ecu pulley and intake i ran a 13.4@106 with my ic pipe coming lose and bogging towards the end. Also check for boost leaks... i had several of them but even after fixing them the boost is not holding to redline. Thats why i am thinking its the mbc.