If you find the vacuum hose in the engine compartment that supplies the climate control system, you could pinch it off with a clamp once you set the EATC to the position you want. This should solve the idle problem if it is a post-EATC vacuum leak. I was thinking the vacuum reservoir on the back of the intake, but I think that is vacuum just for the butterflies.
A vacuum leak might not be the only thing possible; the AC Compressor is turned on in most climate control modes and could be dragging the engine down; you can discount this possibility by disconnecting the pressure switch connector on top of the AC canister, or disconnect the connector on the AC clutch.
You could also try an idle relearn - disconnect the battery for five minutes with the light switch on. When you reconnect, start the car and don't touch the gas pedal. Let it idle for several minutes, while you turn on all the accessories and play with the EATC in all modes. Then finally go for a drive. This might re-learn idle and force the engine management computer to deal with keeping the car running even with whatever the problem is.
