HiCustomer Thank you for asking your question on Just Answer.
Can you tell me how high is "very high"? Do you have any Check Engine light coming on?
Does the idle go back to "normal" after startup?
Wow, that is pretty high.
I would look for some other air leak around the throttle body or the Intake Manifold.
To give you some ideas, I have a procedure for testing the IAC. I know you have already changed it, but there may be some problems still in that area.
This is a PDF file that you can read on your computer and print if needed.
Let me know if you have more questions.
Take Care, Greg A.
The next thing that I would look for would be a mechanical problem, somewhere around the throttle body.
I would check for binding in the throttle lines, including the cruise control.
After that, I would check the other sensors (Throttle Position, IAT, MAP, etc.) that feed the PCM and make sure they are functioning properly.
Do you have a scanner that can display what the PCM is seeing from each of the sensors?