As far as BPV, like mentioned look for a stock one (I have one, but not in the states to ship it, sorry). Or if you are looking run an aftermarket one look at the Cobb XLE (I run it), the Perrin (I dont really recommend, I had too many issues with it), GFB (go fast bits), Forge, or TurboSmart. All make recirculating (like the stock unit), or hybrids (can be ran like stock, 50/50 (or around that nature) or full atmospheric).
"2007 WRX- PPG'd, 20G- Tim Bailey tuned
Stage 2 2005 WRX