If the engine runs and spins the turbo theres theres not really anything that can affect how much boost the turbo produces. Just because it ran on your car don't take it for granted, you have nothing to lose by whipping the turbo off and having a look, you'll be surprised how quick these things turn around and go wrong.

Mine was running a happy 6psi but when i started getting problems someone suggested it may be the clutch slipping, i was certain it wasn't but we turned to boost up anyway to see if we could identify any slipping, then it started hitting the limiter, i turned it down to 2 psi after that, to save some fuel, then not long after when i got a chipped ecu.......i couldn't get it to hold higher than 6psi, took me ages to work it out. It's a very common fault on T3's