If it's the original IAC (which is doubtful, but could be), then the gasket could be cementing it to the UIM. See if you can slide a screw driver under the base of it to pry it off, just don't snap the screw studs.
Also, make sure you pick up a new gasket before you put a new one on there (and you're better off just buying a new one rather then trying to clean the old).
