Hello Scotty I've been having a problem with my 2011 GMC Sierra Denali. My alcohol content goes up every time I refuel using E87. I reset it with my tool scanner and it goes down to 3% and starts like new, but after I have to refuel again my alcohol content goes up to 25% and start rough on cold start until I reset it again. It happens every time I refuel. It doesn't throw any codes and dealer can't figure it out. It is a Flex Fuel and I have tried E85 and still same problems? Any Idea what it could be? I would highly appreciate your help. Thank You So Much.