RacingBryan, bad O2 sensors can cause it to run rich. When's the last time that you replaced them? Do you have any codes from the computer that may cause a rich condition? Check your fuel pressure and make sure it's between 37 and 40 psi. Do a leakdown test of the fuel system. Verify your firing order and that all plugs are firing.
Clearly your idle problem isn't TB or IAB related. You're having fuel management problems. I would leave your idle adjustment setting alone until you get that resolved.
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351W 89 Mustang GT Convertible