You appear to be on the right track. Most likely the IAC. I think it may be time to clean out the upper intake system. Most of these little idle problems occur when hoses and air passages get all "gunked up" with that oily, dirty sludge from the EGR and PCV system.
Spend a weekend sometime and pull the upper intake, throttle body, IAC, PCV, vacuum hoses, etc. off. Then get 3-4 cans of throttle body cleaner and some bottle brushes and have at it. I think you'd be amazed at how much is in there. BTW, depending upon how old those gaskets are, you should have new ones ready to go on. Sometimes, they get damaged during disassembly. It also gives you an opportunity to check for cracked/dry rotted hoses that may need replacing.
TFI modules tend to exhibit their symptoms in various types of misses and ignition advance issues.
I had idle problems and bought a new IAC and the problem was still there. I disconnected the IAC and the car runs awesome. It idles at about 900 RPM's.