[olddog]

From your description, it does sound like the throttle body is sticking and not going closed as suggested by others.

It could also be the idle air control valve (IAC) sticking open.

If the EFI is controlling the spark, there are no springs to check.

With it idling high, you can try closing the throttle by hand to see it that is it. You could also try unplugging the IAC, but if it is mechanically stuck unplugging it will do nothing.

Most IAC are easy to take off and clean up with choke cleaner. I never worked on your system.

I am shocked that the help line suggested the coil. It sounds totally off the wall to me. I see no way on this earth that a failing coil could cause a high idle.