When you get that BPV make sure to check to it, I run it. You need to make sure the pressure on the BPV is correct or it will either sound like you have compressor surge, or wont build boost properly. Its too easy to adjust though. Get the car tuned, run it, see where you are at. If it needs to be adjusted, do it a quarter turn at a time, either softer, or harder.And definetley be sure that the BPV top has at least two threads on it, I blew mine off at 22PSI on a pull, lol.
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX