5.9 started idling quite high

If the plenum plate is leaking you can open the butterflies and look inside the the intake with a flashlight, if there is oil pooled in the bottom toward rear of the motor it is definitely bad. I got the Hughes plenum plate kit and it is fixed for good (not a small job). But... after all that and cleaning the intake and throttle body I still have the 1000 rpm high idle problem myself. Will chirp the tires in the garage putting it in gear. :dontknow: