You either have a vacuum leak, or your idle air control valve is stuck. The idle air control valve is supposed to control the engine's idle, not the screw for the throttle stop. If you take the air duct off of the throttle body, you may be able to put your finger over the round hole going into the idle air control valve, and see if the engine slows down. If it still idles fast, look for a bad hose going to the pcv valve, or one of the other vacuum lines, like the one to the brake booster.