1999 GMC Jimmy Problem

I have a 1999 GMC Jimmy that I am selling but has a small problem. Please bear with me, my knowledge on engines is a bit limited //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif The problem is that it idles pretty high. My uncle, who is a mechanic, ran a diagnostic test on my truck and the throttle position sensor came up faulty (only problem with the truck), so we replaced it. The check engine light is on also. This didn't help, and it still idled about 2100 RPM's in neutral. We adjusted a screw that was located on the throttle body, and this helped a bit. When changing gears, and pressing the gas pedal, it starts at 1500 RPM's increasing normally as it should, so this is a good change. Only problem is that the gas pedal sticks now... //content.invisioncic.com/y282845/emoticons/verymad.gif.3f39c5c2fd57527b671fad3efdfac756.gif Anyone have any ideas how to fix it?

Thanks in advance!