High idle above 3 MPH?

This sounds like you have a vacuum leak, use this guide when the engine is cold to help find it:

https://www.2carpros.com/articles/how-to-use-an-engine-vacuum-gauge

If no leaks are found, let's service the throttle body which the IAC motor is internal, check out this guide and look at the images below to show you how on your truck:

https://www.2carpros.com/articles/throttle-actuator-service

Also, we should run the codes and check out the high idle guide to help see what's going on.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

and

https://www.2carpros.com/articles/engine-idles-too-high

Check out the images (below). Please let us know what you find. We are interested to see what it is.

No engine codes. It is not a vacuum leak, as I stated it runs fine if the speed sensors or anti-lock control module is unplugged. Nothing to do with the throttle body, APPS, or ECU, all have been replaced with no change in problem. Definitely speed related as it only begins above 3 MPH and stops doing it below 3 MPH. Cruise control works fine.

That's a good one, can we unplug the wheel speed sensors one at a time to see if the problem changes? How does the wiring harness look? have there been any modifications? Also, you say there are no engine codes, but have you run the ABS codes?

https://www.2carpros.com/articles/anti-lock-system-testing-and-repair-abs

Please let us know what you find. We are interested to see what it is.