I have a 1996 mustang gt with a Vortech V1 supercharger. The idler pulley went out so i replaced it with the larger one and the new belt supplied by vortech. it was running rough after that and there was a loud chirp when i let off the throttle. i replaced the tensioner, and it runs better, but it still feels bogged down when accelerating and there is still the chirp when i let off the throttle. i think its is belt slip, but a smaller belt wont fit. how can i stop the belt slip?