i was having a problem where i was only hitting 7psi and it turned out to be my boost control solenoid. I got mine on nasioc int he classified section for $20. Do you have a friend with a rex? If you do borrow their bcs and plug it in to your car and see if it fixes the problem. It will take less than 5 min to pull their's off and put it on yours.
CobbTuning.com - How Subaruís Factory Boost Control System Works this will show you right where the restrictor pill should be