Welcome.

I have a similar issue on my '90 Loyale. You IAC valve could definitely be the issue. I've read up on it because, again, my car has the same issue and it seems like if that doesn't fix it, it can be your coolant temp sensor.
What you can do is take off the top hose to the IAC, then take a can of carburetor cleaner and spray it into the IAC. I believe you
should have someone holding down the gas pedal all the way, and have the key in the "on" position. But not 100% sure about this. After giving it a quick spray or two, reconnect that hose and wait about 15-20 minutes and try and fire her up. I had a hard time starting mine the first time after the cleaning, but after pumping the gas a few times, she fired up and seemed to idle a bit better.
If it is your IACV, it should idle better. It's still best to get a new one though. You can always head to a junkyard and pull a clean looking one off of a low mileage Soob. I believe it's four bolts, that hose, and an electrical connection. I have yet to do this to my car though. Or you can take yours off your car and give it a good cleaning. Still, best bet would probably be grab one from the junkyard, clean it, then install it in your car.
If it doesn't affect it at all, then look elsewhere.