The reason I asked what I did is because very often TBs, OE or aftermarket, come with a thin elastomer seal in the throttle body bore intended to almost completely seal the throttle plate when it's closed. This forces all the idle air control to the PCM via the IAC motor.
If that seal is damaged or removed because someone went into the throttle body with a toothbrush and solvent it's possible that the TB blade is now leaking too much air and the IAC, even when closed, doesn't really have control over idle speed any more.
FWIW, Ford does not recommend cleaning its throttle bodies. In the Ford Service Manual I've got, Sec 303-04B-5 states: "Caution: The throttle body bore and plate have a special coating and cannot be cleaned." This is why...
Ditto for throttle plate adjustments: If the plate closed-position screws were messed with then, again, the plate may be open too far and allowing too much air into the engine, resulting in the same effect.