Ya so i got a 01 Gtp i bought 2 years ago and i love the car. I just need some info on mods to do and no to do. current / K&n cold air intake .... 3.4" pully (lost my breather nut !?!!?!?. ) msd coils. catback ,u-bend and resanator removed . im trying to get a lil more out her my car and get it to run good . the check engine light is on and it comes up air/fuel measuring. i never had the pcm or car tuned could that affect anything. breather nut?