I have a 2002 denali with 18,000 miles. When starting hot the idle "hunts" between 400 to 600 rpm until I goose the throttle then it clears up. any ideas?

I guess it would be normal for a vehicle of such size at low RPMs

otherwise check your throttle body

Some of the 01 and 02 trucks have a low idle complaint. Since your truck is still under warranty, take it to your dealer.
I don't have the bulletin number handy, but there is a bulletin and/or a calibration upgrade for some models.
Sometimes, cleaning the throttle bore will fix this complaint. (should be done at no cost to you as it is a warranty concern)

MY 99 GMC had the same problem. It was the fuel pressure sensor. Not a hard fix. But since your truck is still under warrenty go back to the dealer. you might want to check out the following web site.

http://agmlemon.freeservers.com/

Its a GMC lemon site and what to do if you want GM to buy back your GM