My 1999 F150 4.6 5 spd is having high idle between shifting and while coming to stop. Cleaned throttle body, replaced PCV valve, TPS, AICvalve (aftermarket), checked for vacuum leaks (none found). No check engine light, temp gauge works fine. I took it to the dealer and they ran diagnostic and told me it threw a code "bad AIC". I then ordered a Motorcraft IAC valve and installed it a few days after it arrived in the mail. Still idles high, no change. Looking for some suggestions? Truck has just 140,000 miles and I am original owner. Tuned truck up around 90,000 miles, runs great except for high idle which is driving me nuts.

Joe