In the process of getting my stubborn bastard of a black car tuned, and YES it's being fussy. Pulling vacuum in the 10 in/Hg area, split LTerms at idle, the works.

Here's the thing. With NO changes other than some playing with the throttle stop to try to fix the split LTerms and set the IAC a bit better, the car just started to act funky. Surging around down low with the IAC maxed out at 160, but then after it started to warm and the target idle started to come down to about 1050-1150 the IAC started to shut, and the car eventually settled down to a solid stable 1050 idle with the IAC set at about 20-30. BUT, the instant the computer went into closed loop, the car idled up to 1800 RPM while the IAC went to zero.

Figure that one out, because I can't.