I purchased my 02 WRX in February & I think it has been having a problem with the boost not being 100% consistent. I am probably wrong in my thinking but I think I have a leak in my inlet hose.
In 1st, 2nd, & 3rd gears, it will reach only ~10psi of boost. I took it to the local drag strip (1/4 mile) & ran it a few times & it always ran at this boost. Off the track I played around with my car & every now & again I could hit the target boost of about 17psi in 2nd & 3rd gears. I have not really checked any other vacuum lines or hoses to check for leaks there so it may be one of those but they visually look fine.
I have also done a 3rd gear pull & it reached the 17psi around 3500rpm-4000rpm but did seem to taper off afterwards (I may have let off the throttle too)
Stock Turbo Inlet Hose
Stock Engine Internals
Current mods are:
Weapon R Intake
Apexi N1 Exhaust
TurboSmart Manual Boost Controller
Maybe a aftermarket midpipe