At one stop light the IAC clicked up several ticks and I could hear the sucking sound and noticed the increased RPM. Once again, I think the ECM is trying to compensate for a below set-point idle speed so the IAC overcompensates. The A/C was on at the time and that old A6 style compressor really puts a drag on the engine. Combine that with the variation I see in the idle speed screw setting and it's easy to imagine the ECM is doing some wacky stuff.
Do you have a vehicle speed sensor? IAC control on the 7747 can be a PITA, especially without a VSS.