ok after looking at the throttle body online, that screw probably doesnt adjust the throttle position, but it MAY adjust the sensor attached to it. this might be why its idling high. that said, it shouldnt have really affected the idle at all, and that screw probably only adjusts the 'idle' voltage sent to the ecu which is calibrated from the factory. short of opening it up, you wont really know.
but if you were going to muck around with it, check the idle voltage (while engine is at operating temp) BEFORE you stuff around with it. maybe adjust it down a few 0.xs of a volt to see how it goes. if it doubt. put it back where it was before.
maybe a few cars can measure their idle voltage and post it in this thread. both 'working' and 'not-working' cars.
also might be the engine water temp sensor is stuffed causing the high idle thinking the engine is still slightly cold and keeping the revs up.