I thought I would give an update and pick some of your brains as to the idle issue that I am now having. I haven't been working on or driving the car much lately because I have been so busy and I am still having a mild rough idle issue.
Since I started this thread to address the above discussed idle issue, I have replaced the IAC, spark plugs, cap and rotor, O2 sensor, adjusted the TPS switch, and checked the coil resistance. The original issue was that the car would not stay running at idle, it is now running at idle but with the occasional (every few seconds) misfire. Other than the misfire at idle the car is running really well. It idles relatively smoothly, the IAC is definitely functioning correctly because the idle fluctuates smoothly and regularly especially with the A/C on, it is smoother than it ever has been throughout the rev range, and it also has plenty of power on acceleration.
My father, who has been a mechanic for over 30 years, but admittedly gave up on Alfas a long time ago, thinks it sounds like a lean idle issues, possibly caused by a vacuum leak. Considering everything else that I have checked and replaced, confidently ruling out an ignition issue for the most part, this sounds like a promising place to start looking. Then I was thinking, if the original rubber boot that seals the IAC to the intake had aged and formed to the original IAC, would disturbing it and using it with the new IAC possibly cause a vacuum leak? I am also thinking that my original assessment of the new IAC and its slightly crooked internal baffle (pictures above) could be causing the same issue, too much air at idle.
Any ideas or suggestions as to what my issue could be or where I should start looking?
Thank you, Steve