start the car. make sure the idle is acting up and get a can of break kleen and spray a mist about a foot or two away from all the vacuum lines and intake manifold. If there is a leak, the car will stumble even more when the mist finds it.
Is the idle air control valve exactly below the Throttle Body? Is it the one with 2 small coolant bypass hoses going to it? ^ if it is, did you replace it with a used one or new one?
^ if it is used, did you check it with another car to make sure it doesn't have the same problem?
^ if not, or you don't know, you have to take it apart and there is a nylon screw inside that has to be turned clockwise to tighten it up. It allows coolant to bypass through it and bumps idle up until the coolant warms up. Once the coolant is warm, idle will come back down. if the nylon screw is loose, it'll cause the surge in idle.
If you live in socal i can help you out.
vito