I just recently noticed this today and it wasent doing this before.
But say after i shift or downshift or something. The revs climb down but stay at like 2 grand at a dead stop or a bit lower or higher than 2grand. My buddy then said to give it a rev and see if they drop back down to normal, I did and they fell back to under 1000 like normal. Can anyone explain this? he said something about throttle sensor being stuck.

 

might be your butterfly valve in the throttle body.

 

get some throttle body cleaner, take off the intake from the tb and while u give it gas from under the hood spray the tb cleaner in the tb but dont drown it all in one shot do it in segments...then replace your spark plugs cause it fouled mine...but all in all it worked out good for me nice smooth revs now...