When I'm in gear and I shift to Neutral, the rpms don't drop to idle level. The truck just stays spinning at what I was going before. I really don't have a lot of experience w/tq converters, but maybe that is staying locked.

Any help would be appreciated.

 

is this while you are still moving? why are you doing this anyway? it is probably just the throttle follower holding idle up high while you are moving. GM did this on purpose to keep you from loosing power assist (steering, brakes) while you are moving.