I have a 2011 Silverado with 5.3L. at 75,500 miles I had no issues and averaged just above 17mpg. At 76,000 miles the check engine light had a code of P0305, which is misfiring on #5 cylinder. I have followed all of the manufacturers' maintenance requirements including the oil changes to the specs.
Auto shop opened the manifold on the driver's side and it smelled like a dead animal, oil had silver specs and the lifters were worn so much that they would not hold their position. Seriously, disappointed in the 5.3L engine with the fuel mgt system. I am glad to hear about your success. I need to pursue the fix.
