2001 GMC Jimmy throttle sticks

That would be typical of a vacuum leak. Look at the throttle blade where the cables are attached to be sure it is coming back to its stop. That will eliminate any suspicion of a sticking cable. Next, with the engine running and still cold, spray some water over the vacuum hoses and intake manifold gaskets. Watch for anyplace it gets sucked in and the engine slows down momentarily. You can also pinch off various vacuum hoses to see if one brings the idle speed down.

Try pinching off individual vacuum lines. If one brings the engine speed down, do the same thing on the lines where they branch off until you narrow down the offending line. If none affect engine speed the intake manifold gasket could be leaking. You may find that with water if it's up on top. For hidden leaks you can rent or borrow a smoke machine to inject white non-toxic smoke at 2 psi into a vacuum port or hose, then watch for where it sneaks out.