I have the same issue with my 96 contour. I havew changed the MAF, Cleaned the IAC, Fuel Filter, Air filter, Checked countless items.
I was wondering what the gasket looked like when you installed the new IAC. Was it like 2 O rings or was it a big gasket covering the entire mating surface?
I also was wondering if you checked the spark plugs I have heard this suggestion many times.