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If I have a car giving me trouble with an idle, the first thing I do is disable the IACV completely and boost leak check the engine for pressure leaks. If it still bounces around, the next step is disable the timing control (lock the timing steady). If the engine is still having trouble, manually verify the locked timing for each cylinder using 90* timing marks to ensure each one is sparking at the right moment. Then, you are looking for combustion related issues, fuel pressure, checking spark plugs, cleaning injectors, time to start thinking about a camshaft related issue or other airflow related source that is not controlled by the computer.
Then work backwards. Once the idle is stable with a locked timing and no idle control motor, you enable the timing and tune the map for stable idle control timing. Then you add back the IACV function and tune that. The idle control motor is the icing on the cake; shouldn't need one to maintain a steady idle, it just helps raise and lower the idle for temperature, any added idle control function is a bonus feature (icing). You should not be looking at it for idle stability as a sole, primary function. That just turns it into a bandaid, the opposite of icing.
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