I did the silencer chop method. Kept the Y-joint in, but chopped the rest of it off. So the ram-air helps kick more air into the fenderwell. As far as warranty goes, i don't think they'd ever notice it wasn't there unless they took out the wheel-well cover. Do a search on "silencer removal" or "silencer mod", there's tons of info. I pretty much followed the steps at
projectwrx i think. It's really easy and I don't know squat about cars. Haven't really noticed any hp differences, but you get a nice whoooshing sound when yer givin it some gas... sounds pretty cool, and not abnoxious at all.