High Idle

If the idle is that high I would suspect the PCV valve has failed. Replace the PCV valve and see if the idle is better.

Sorry, I did not see that you have the 5.3. If the idle is that high you must have a check engine light and a code. If you can tell me the code I can help. If there is no code I would suspect the following;
bad mass air flow
bad map sensor
vacuum leak

Okay, if you can get the codes scanned again and let me know the code number I can advise.

Most times if there is a throttle body or pedal sensor issue there will be a "reduced power" message on the dash. The common items are the pedal assembly or the throttle body or the connections to each.

That is not enough digits. There will always be a P followed by four numbers.

If the reduced power message went away then that is a step in the right direction. You can try and relearning it by turning the key on and not starting the engine. Press the gas pedal all the way to the floor and let up. Shut the key off and then start it. See if it helps.

Okay, does it accelerate fine now?

The code P0507 just means that the throttle body cannot restrict the rpm to at least 200 rpm's from the desired rpm. So if it cannot the possible causes are vacuum leaks or deposits on the throttle body or a failed throttle body. Since you replaced it if the issue keeps happening then the engine needs to be checked for a vacuum leak.

The idle will be whatever the engine computer wants it to be there is always a possibility of a failing motor in the cluster so the rpm is not reading correctly.