just replaced my iac today and that was a main cause for my problems. tell you what you do - remove the IAC (it is on the right attatched to the TB) by two 8mm bolts. Now, put a thin piece of cardboard as a gasket kind of but with no holes in to bypass the IAC totally (screw the iac back into the tb so the pressure keeps the cardboard between, sealing off the iac completley from the tb). now see if the car's rpm drops.
Also, while the IAC is out, you can do 2 things to test it.
#1 measure the resistance between the two terminals. it is not plus and minus they are connected. my 2 bad iac's made that beeping sound (to let you know that it is one connection), but the brand new one from ford did also, but I got a 10.0 on the voltmeter. So I realized that the bad ones were shorted out.
#2 this is more practical. put your mouth on the one hole and make sure your lips are sealed and blow...
what's wrong with you guys (perverts)... no seriouslly, if the IAC is bad you will be able to make air go through the other side (make sure it is going from before the throttle plate to the other side, and not visa-versa). both my bad ones did that. if the seal is good, you wouldn't be able to empty your lungs. Oh - heh - and you may want to clean the IAC off b4 you do that - I didn't really care - I like the taste of dirt haha j/k
hope this helps
ps - go for FORD - it may be more expensive, but none of the other ones work right