When you say that your TB is grounded, is it grounded with it's own ground wire from the TB to the firewall or the side of the fender like a bunch of us have done recently? A lot of the members here have cured their idle problem with that, myself included.

 

I had rev problems a couple years back and i too ended up going to dealer after going nuts trying every possible solution but it ended up being the throttle positioning sensor.It only cost me $90 parts and labor but after finding out how easy it was to replace I was ticked off.