I hope it's 500 and 650 RPM at idle.....an idle of 6500 RPM is really gonna limit those highway speeds.

My old 3.0L used to idle around 900 or 950....obvioualy high. After playing with it for a while I figured out the shaft on the throttle butterfly valve was worn out and that was causing the throttle to not close fully.

It's easy to test actually. Get the truck running and just reach in there and push the throttle closed (push where the throttle cable connects to the lever arm) with a little finger pressure. If the idle drops and stays there after you remove your finger, it's probable a worn butterfly shaft.

I was all torqued up to replace the throttle body....but then I realized, aside from the high idle, it really wasn't effecting anything.....and not worth the $350 the junk yard wanted for a used one.