My mustang has serious problems idling, I have had this combo for about a year and no problems, I have no codes, but I replaced the IAC, EGR, EGR pos sensor, TPS or whatever its called. If there is a code lurking in there will disconnectiong the battery clear it? It does seem like there is slight power loss maybe im just imagining and it just sounds different at idle I dont know, like its loping alot more, I never used to have these problems. Sometimes its fine, and other times it surges dies when I turn with the clutch in its like its posessed. I cleaned out the throttle body, and ran fuel injector cleaner through it, the injectors only have a few 1750 miles on them as well as the TB the bottom end has 62000 miles on it no smoke besides brownish black (slight) at WOT. Oh I do have a fuel pressure reg set at 41 psi.