I'm using the FIPK GEN II kit as well as the Calmini cat-back, and I swear sometimes that I'm driving a different truck. Not kidding about the throttle body spacer though...that hiss takes some getting used to. I'm considering putting heat wrap on the hood and putting sound mats in the doors just to help get rid of it. I might go with the full SLR Throttle-body instead of just the spacer to get some relief from the sound. We'll see :rolleyes: