Since you say it idles well I doubt the IAC.
I'd like to know more about just what the enine does when it acts up. Sounds like it is at temp when it does it's thing.. lectric items usually start acting badly when at temp first before going completely south. Coils and condensors are notorius for running good cold.
Also could be a spark box as they do the same. In fact I'd start there.
Big Jim <img src="/forums/images/graemlins/pfft.gif" alt="" />

professional bovine relocation specialist