Could also be the PCV hose to the throttle body (if it's just 2000 rpm after warm up), mines been idling high, I made my own replacement today, but before that...
This happened earlier. Picked one of the kids up at school, on the way home coming up to a red light, I felt the car wanting to "go", the closer I got to the stop line, the harder I had to press the brake, then I noticed I was standing on the brake pedal and it wasn't going to come to a complete stop.
- killed the ignition.
- put it in park, started, revved up to 4500+ and something kicked in to keep it from redlining, but it wouldn't go down, even when I punched the accelerator a few times.
- waited for the light to go green and started and jammed it into drive as fast as I could, burned rubber, headed for the nearest turn off and parked in a parking lot, popped the hood.
- *checked the vacuum hose on the passenger side (it runs behind the coolant overflow res.), made sure it was tight,
this happened to me before when I'd knocked this hose off while tinkering under the hood. Started the car ->4500+ rpms still
- popped off the cover and noticed that the PCV hose was mostly hole, ...but I didn't think that was it. It would explain the high idle though, ...but not this craziness.
Wggled anything that looked electrical, -> 4500+ still
- Grabbed the cable linkage cam thing and rocked it back and forth, started the car, back to sanity (sort of, the 1500-2000rpm "warm" idle with the toasted PCV hose), drove home, dropped off the kid and got a piece of hose and an adapter to repair the PCV hose, ...back down to <1000RPM idle.
Picked up the wife from work (I wouldn't let her drive because of the

problem), and just before I turned down our street, ...I could feel the car wanting to take off again. Pulled into the driveway, threw it into park -> 4500+ rpm.
So after a while I went out and checked for error codes, nada, I did notice the cruis indicator was on, so a batted at the lever a few times 'til it went out, ...started the car, sanity again.
Either; the TB is gunked up, or one of the cables is getting hung up,
or the cruise control is f'd up and has a mind of its own, or a sensor fail, or a TPS fubar?