Hey, my 2007 Sierra 5.3 AFM with 90,000 miles has already had a tray put in the oil pan, engine flushed, new spark plugs and wires, and as we speak, having new rings and pistons installed. The service mechanic in the beginning said everything they were going to do to my truck wouldn't fix the problem. He said the only fix would be to install a new engine (which will be the next step on my truck). Apparently the dealership has replaced alot of motors according to the service mechanic. I should get my truck back later this week.
Thanks
Nick