Ben,
Defenitly sounds like your IAC. Bring it over on Saturday and I'll take if off and clean it for you. I had the same problem and so I went to Autozone and bought a new one that wasn't Ford OEM, worst choice ever. Car idled wayyy high. I then cleaned my old one and put it on with no problems ever again!
You could use an entire UIM/LIM cleaning for sure! You will need to order new gaskets and it is ideal to have a few days without your car so that you can let the manifolds soak and scrub them out really good. The upper is a PITB to clean!
Jeff