I know you are dealing a lot with the IAC but I would suggest that is not the problem. Start the motor WITHOUT jumping into base timing. THEN jump A/B to get into base timing and THEN manually turn the distributor to get 8 deg BTDC. Remove jumper and see what happens. Idle will usually increase during base timing, that is normal. If it runs away after pulling the jumper you likely have a vacuum leak. Double triple dog dare check the TB blade is fully closed and throttle linkage allows it to close fully as well.
it was the IAC, that was pretty much my giant vaccuum leak. Took TB off and was stuck wide open. found a connection at the pcm, replaced wire and boom. back to working. service mode worked like it should and all is well....with this engine now,. haha. other engine has a hard miss out of nowhere now. fresh injectors, new plugs. verifed spark at all cylinders. hoping rocker or spring
