My 03 GMC Durtymax 2500 4X4 Extended Cab smokes like a bonfire with wet grass at idle. It cleans up at cruise and gets great mileage otherwise. But let it idle for a few minutes and you may think the swat team is smoking out a bad guy. Anyone ever heard of this? If so your help is appreciated. I have had it back to dealer twice and they have not offered any suggestion.
Thanks, Matt