I Have a 03 gmc 6.0 with 105,000 miles on it. For the most part the truck runs perfect. The problem is when you stop for a stopsign or redlight the truck will go down to 200 rpm and sometimes stall. When it doesnt stall it goes quickly up to 5/600 and idles fine. If you just start the truck in the driveway, it starts fine and idles 5/600 fine. Its just when your in the gas and come to a stop so to speak. There is no problem lights on the dash, and when hooked to the computer it is throwing no codes. There is no leaks in the intake, it has new wires, plugs, air, fuel filters ect. Anyone have any ideas what could make the idle low? its not going to work the way it is for snowplowing lol....IF ANYONE HAS ANY EXPERIANCE WITH THIS PROBLEM IT WOULD BE HUUUUUUUUUUUUUUGELY APPRECIATED, THANKS!!

aftermarket throttle body? is your PCV system clean? is the throttle body clean?

Pull the throttle body and clean it: all around the butterfly and such. Check the PCV hose for leaks and make sure it has the correct PCV valve, part number 12572717.

Cleaned The Throttle Body And Bingo, Problem Disapeared, Thanks Guys!!!!!