have you checked your tps? Cut the wheel all the way one direction and hold it and turn the A/C on and see if the idle stays the same. If it does your iacv is functioning properly. My guess is that something is telling the ecu the wrong thing and it's telling the iacv to open a little too much.
I just read what you said about the clutch. If you put a load on the motor and it dies your iacv is not functioning properly...period.