anythin non restrictive will do the job mate iv got a mushroom hks great big thing that came with the kit 1 thing to watch though make sure its not too long because it goes at the bottom of the bumper between the wheel and the little grill look in the bottom left of the pic i might have an fk cone filter lyin about if i have its yours if ya want it http://img.photobucket.com/albums/v178/eatthis/17082007134.jpg