Possibly too much boost?
I just purchased a 2004 wrx and recently put a glowshift boost gauge in it. I noticed that the gauge reads close to 16 psi in 4th and 5th and around 14 in 2nd and 3rd. I know the gauge is cheap and could just be the gauge reading inaccuratly. But I noticed that the heat shield was gone from the turbo and the lock nut on the waste gate actuator arm was turned way out so it was not "locking". So the previous owner may have adjusted the wastegate arm to achieve more boost. I would like to know if I should re-adjust the arm to get the boost back to around 13 psi in higher gears.