Hello everyone i'm new to the forums with a 1989 5.o GT 25th Anniversary model i recently picked up and this looks like the perfect community to join for what i'm looking for. I'm having issues as far as the engine running a bit lean, idle and deceleration of the throttle; mostly when in neutral or revving with the clutch engaged. It climbs down extremely slowly and has a running idle of 1600 rpm's while in neutral and 1400-1500 rpm's with the clutch engaged in gear. So far i have removed the throttle body and all components except the TPS for cleaning and i have replaced the EGR and IAC with all new gaskets. I have also ran it without the IAC valve plugged in and i get a better idle; around 1200-1300 rpm's and a way better throttle response as far as deceleration. Now for the fact that the IAC is brand new, the throttle body is nice and clean and it has all new gaskets i'm gonna assume the problem lies somewhere else. So my questions are the following: What in the chain here could cause this slow deceleration issue, Does my idle need to be adjusted or is something out of adjustment that makes it idle high and what should the idle be on this particular stang? TPS have anything to do with running lean and higher idle? Any help would be greatly appreciated! Also as far as what i know, its equipped with an aftermarket cam of some sort, distributor, oil pump, edlebrock intake manifold & throttle body that i believe is a 65mm bore. I'm not sure exactly if being a bit more high performance effects what a base idle should be or not so i guess i'll throw that in there.