After removal/installation of engine/transmission for trans repair my engine now has a very high idle and while idling every couple of minutes the engine sounds like it is going to stall. I've eliminated vacuum line leaks by plugging ports on the plenum and I've replaced the IAC valve to no avail. Could I have cracked an intake gasket or even a head gasket while lifting the engine. The lift points are on the heads.I tried to be gentle with the wiring but it is an old car and I'm afraid the insulation may have cracked off. When I unplug the IAC the RPM's come down to what seems right.. I also replaced the VAPS rack and pinion while I had access to it. Where should I be looking for the source of the problem?