First off I would not do the BOV. You could do a CAI, turbo inlet and that would allow you to hear the BPV. Common issues that you will run into on the older WRX is that the uppipe is catted and needs to be replaced with a catless uppipe. The trannys dont hold alot of power over stock but if treated right will do ok. I know alot of WRX guys that has a pretty good amount of bolt ons with no problems with the tranny but I know a hand full of guys that pushed them a little to far and had to rebuild them. They are fun cars to drive and modd but they need to be tuned with every upgrade to run and last.