[NachtRitter]

Thanks Clev, I'll check into that. It's not high idle *all* the time, but it kinda bounces while I'm coasting with engine on (I typically do that at night time or when the weather's bad) between ~900 and 1200 rpm (occasionally as high as 1500), and is a bit higher than normal when I'm stopped (~1100 rpm). Sometimes, if I'm stopped long enough, the idle gradually works its way down to ~900.

What throws me though is only one of the 3 ECUs I have seems to have a problem with the idle. The original Cali ECU works fine (even with my conversion harness installed) and the new Fed ECU I found this past weekend also works fine (though I haven't put more than 40 miles on the car with the new Fed ECU). Only the first Fed ECU (which I put in a few weekends ago) behaves differently. The model numbers on the two Fed ECUs are the same, so it is a mystery to me right now.