I have the K & N tornado sri on mine, recently has been stuttering,especially with the air on. did not do this with the stock air filter ?!?!? I am thinking about buying the fswerks cai. i did put auto lites 103 copper on mine and that did smooth out the idle, cheap too.... it has been really hot here in michigan, upper 90's. hate to really drop another 200 for a cai...