This has been a common problem on these models. My 06 was really off when new. Some are worse than others. When I replaced the tank on the warranty gas cap breaking my new tank doesn't lie as bad! You can take the float arm out and bend it down a little. You should remove the tank and take it out the front and not just try to bend it from the cap hole. There is a mechanical gauge that fits; I think it is the 08 D8. If you go this route, you will still have to deal with the odometer counting over and you can't see your miles.
