Since you feel it when you place it in gear, have you checked motor and trans mounts to make sure they are in good condition. When you put the car in gear, it puts a load on the mounts and if one is bad, you may just be feeling the engine vibrations.
As far as the IAC, it really only maintains idle speed and wouldn't cause a rough idle.
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Friday, May 30th, 2014 AT 7:49 PM