The throttle stop screw is just to keep the butterfly (throttle plate) from slapping the TB throat. Changing the stop screw throws the TPS, out of adjustment. But the TPS is pretty forgiving, the by spec. adjustment is always best, but it will work OK, when a little off (ECU and TCU compensate some).
Most times the problem is a sticky or really dirty IAC (idle air controller).
Sometimes a stuck open EGR valve or faulty transducer, you can check that by plugging the vacuum line and seeing what happens.
O2 sensors will also sometimes cause crappy idle, it will often change, or hunt at idle, the idle cycles up and down.
A small vacuum leak can also cause a rich and crappy idle, you get a little extra air at the front of the intake manifold, at the vacuum tree, which fools the O2 sensor into a rich condition (can also be caused by loose intake manifold bolts and/or a leaky gasket. A larger vacuum leak will usually cause a high idle.
Mine was actually all of the above, which added up to a really poor idle.
Search idle adjustment, there was a thread recently, where a guy recommended, adjusting the idle by the idle adjusting screw behind the metal plug on the drivers side of the TB, with the TPS properly adjusted and the IAC fully closed and unplugged. There is an idle bypass orifice, with an adjuster, that's factory set, though the orifice does get plugged up and the factory settings, were for a fresh motor.
Lastly, the engine temperature sensor and the MAT (intake manifold air temp. sensor) have a large bearing on idle. But if they have excessive resistance it usually causes a higher idle and/or a rich running motor. But the harness for the engine temp. sensor, the knock sensor and the O2 sensor, goes down the front of the motor (from the front end of the fuel rail harness) back under the motor and sometimes fries on the exhaust manifold or chafes on the frame and suspension parts. No telling what problems this will cause.
