One problem related to engine exhaust system has been reported for the 2011 GMC Sierra. The most recently reported issues are listed below.
I own a 2011 GMC Sierra 3500 6. 6 duramax diesel truck. When the truck is "regen-ing" the "dpf", raw fuel leaks from an exhaust coupling located at the turbo and down-pipe saturating the hot exhaust pipe with fuel. When you come to a stop while it is in this regen mode white smoke boils out from under the hood and enters the cabin inducing a coughing fit and burning eyes. I took the truck to a GMC dealer in san angelo TX and told them about the problem. Was told that they couldn't replicate the problem that I was describing and that I should rest assured because "diesel won't burn anyway".