One problem related to fuel delivery has been reported for the 1998 Audi A6. The most recently reported issues are listed below.
Back pressure develops when refueling with the engine and ignition off. Gasoline gushes out onto attendant, car and ground. Obviously, there is a risk of injury or death from fire or explosion. This has happened many times , so that we no longer fill our tank, as its not nearly as bad if we fill it only 3/4 full. It will still spray out, but not gush out. This is a serious problem which Audi refuses to acknowledge as a defect, even though lives could be at risk.