Ok let's try to eliminate the MBC as the source of the problem. Take it off and route the lines normally. If you unplugged the BCS then put that back on or you will run infinite boost = bad.
If it boosted around 11-12 psi, then obviously your MBC is at fault. Take it back for a new one and make sure the lines are correct and the screw is fitting in correctly.
If you still only boost 7psi i would think you have a MASSIVE boost leak. Run the boost leak test as shown in the VFAQ and come back with the results. Even small boost leaks can make our cars run like shit, that's just how it is. Pressure test up to 20psi and fix all the leaks.
If it STILL only boosts to 7psi after you fix the leaks, check for exhaust leaks. Take off the manifold and turbo and use new gaskets if necessary.
If all of this doesn't fix it, post here and we'll see what else we can do.
