im more than happy with my K&n 57i, i know alot of people on here prefere the standard airbox and panel filter route but i personally dont see the point in it at all in terms of performance upgrade, i know a induction kit will not give a gain in bhp if we are all gonna be honest, but it did make my car run a hell of a lot better and it sounds great, and will last forever too.
just make sure you feed cold air to them and u cant go wrong..