Hey mate, yeah it does look a bit down on BHP compared to Yosser, but look at the torque, there is nothing in it between yours and his. Torque is what matters not bhp, bhp is just a function of torque and revs ( IIRC ). Anyway if you want 12psi then why not get a MBC and a accurate boost gauge ? Might be cheaper than chasing a fault that may not be there, its possible that your car has never run 12 psi.

Are you sure you dont have a boost leak some where ?