[ssmith95]

I talked to Marc this past Friday and he confirmed it is the ECM. He is sending it off for repair.

Just to recap in case anyone runs across this thread down the road. This was a real pain to diagnose because I kept find vacuum leaks. I had a split hose going to the EVAP solenoid and the rubber connections going into the check valve for the cruise/ac vacuum circuit were leaking.

The IAC pintle not seating as described in Marc Haibeck's "Find and Fixing Vaccuum Leaks" paper was the first hint that something was not right, but I somewhat ignored it. After testing with a smoke machine and not finding any leaks, Marc asked me to check the IAC. Around this time is when I discovered that putting a rag in the IAC section of the throttle body lowered the idle down to an appropriate level. I drove the car around 100 miles after all of this and it became pretty apparent this was an ECM issue. Sometimes the car would close the IAC all the way, stalling the engine out. Other times, it would idle high, sometimes falling, other times hunting around. In other words, totally random behavior.

I'll update this thread when I hear back from Marc on my ECM, fingers crossed that it's repairable. Thanks again for everyone's help.