Mine did the same thing...after cleaning IAC, throttle body and MAF Sensor still did the same thing.

It was the most common vacuum leak area on our trucks. Check your PCV hose behind the throttle body (way in the back).

http://www.autopartscheaper.com/1997...FZTm7AodPDoAIw

 

I've replaced everything but the computer and tested the vacuum lines and no leaks the brake booster is good and still high idle at any speed and throttle body was cleaned up

 

Even though this thread is three years old, you still get me to bite on your line trying to help.
Did you ever think about looking at live data with a Scanner instead of just replacing parts hoping the get lucky?
What causes the engine speed to change?
Additional air.
The high idle has to be from that, nothing else. It's what you do with your foot on the throttle when driving. Same thing.
What would add additional air?
How about the following;
IAC open farther than normal at idle. It is fully open above about 1500 rpm so is not the cause unless there are two issues at the same time.
Vacuum leak into the intake tract as unaccounted for air metering. There would be a CEL light and codes set.
Gasket, loose throttle body, Throttle not returning to normal idle, vacuum leak in the rear of the throttle body PCV connection.
Any codes anytime?
If yes, are they 171/174 codes? If yes, there is an air/vacuum leak that has shifted the fuel tables more than 25% causing the codes to set and possible rough low speed running and stalling?
If no, there may be an air leak around the throttle body.
Is the engine running temperature too cold like 180 degrees? Should run at about 200 degrees +/-.
If yes the computer has the IAC open farther than it should be at idle adds fuel and changes the ignition timing. This trouble is either a faulty CHT or Thermostat is stuck open.
Point is you have to look at the technical operation rather than just replace parts.
Do some checks.
At hot idle is the rpm well above 750?
If yes, remove the IAC connector. Does the idle drop?
If yes the IAC is working. If no, the IAC is either stuck open or commanded open or there is a larger air leak into the intake tract.
This will be a start in tracking down the cause.
And looking at the live data with a Scanner to see anything out of normal range.
Good luck.

 

Yeah, shoulda started your own thread. Maybe you would have given somebody a clue as to what you're driving. All engines and year models are not the same. For the old EFI 302 engines, if you cleaned the throttle body while still on the engine- there's yer high idle. The solvent used to clean the throttle body will eat the intake gaskets. Bad gaskets= unmonitored air coming into the engine= high idle. The intake manifold has to come off and the gaskets replaced......if it's an old 302 EFI.

 

He has a thread going already, with replies.

https://www.f150online.com/forums/19...dle-issue.html

Looks like he replied here instead of there. Very confusing, reported to mods, no action taken yet.