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I would do 2 things. First clean the throttle body by removing the intake snorkal and scrubbing the backside of the throttle plate and surrounding housing with an old tooth brush and some carb cleaner. That should stabilize the idle control.
Next remove the EGR valve and check it for any chunks of carbon stuck in the pintle and holding it open.
You didn't mention a check engine light so I assumed it's not coming on. If it is, have the codes read. That will point you in the right direction. If you have any further questions on the subject after accepting my answer, feel free to ask.
Did you remove the EGR valve and look at the pintle?
Did you look at the back side of the throttle plate?