To make a 6 month long story short. When I first installed a new boost gauge, my 7 was running with only 7-6-7 psi boost. Needless to say I began investigations with my specialist. These resulted in the substituation of all vacum pipes and upper manifold gasket.
Still no improvement.
We continued diging in till we arrived at my suposedly reserviced turbos. Fouond out that the engineer responsible had not changed the main shaft so the central ball joint had gone bad and shaft was unblanced. I reserviced the turbos (for free ) but still only a slight improvement 8-7-8.
Continued found a leaking BOV which was substituted another imorovement to 9-8-9psi.

I still was not satisfied but we had checked everything but I still insisted. Finally this week we found the guilty. It was again the engineer. When reservicing the turbos he substituted the short lines from the primary turbo housing to the wastegate and pre-control actuators without knowing that the speed pill (restrictors) where in there.

Now I can enjoy a perfect 10-8-10 psi by slightly touching the accelerator pedal even on third. If I push in hard I can arrive even to 15psi.

So check for the pill when you reservice the trubos.

 

Your mod list suggests that 15psi is a dance with detonation and more. Do you have upgraded fuel system, and have you changed out your ECU?

Dave

 

To me it suggests that his WG isnt opening at all