the throttle position switch does not adjust idle, but the idle adjustment screw is very close to that switch. on an 83, it should be down inside a small shaft. This shaft is molded right into the intake manifold near the throttle body. It may need some WD-40 down in there as gunk can get in there and stay.
You'll need a wide flathead screwdriver to adjust it. The throttle position switch adjusts your fuel delivery for different points on how far your throttle is depressed. You want to set your idle, then plug in the throttle position switch and loosen the two mounting screws on each side just a little so you can rock the black box back and forth. Turn it all the way to the right (clockwise) then with the engine runing, bring it the other way slowly and listen for the idle to change just a little. Probably will go down. This is where more fuel goes in. adjust the sensor back clockwise just a little bit before this extra fuel goes in. You want to be able to just tap the throttle without it hitting the first sensor for extra fuel. Tighten down the two screws on each side to hold it in place. Don't overtighten them as it isn't needed and you are screwing into aluminum.

If you adjust the throttle position switch too near the first contact, the only drawback is a slightly more jumpy toe-in throttle response. With a stock throttle body you might not even notice. My large throttle body is very sensative to things like this.