Accelerator Stuck problems of the 2004 Audi Quattro

The contact owns a 2004 Audi Quattro 4 (n/a) the contact stated that vehicle gas pedal sticks. The first occurrence was about 3 years ago. The contact was entering highway going about 60 mph on a dry day , he took his foot off the accelerator and the vehicle just "took off". He managed to get the vehicle stopped. The problem has reoccured on and off since then. The vehicle was taken to dealer and the technician stated that the problem was the floor mats. The mats were re-adjusted and the problem continued. The contact took the vehicle back to the dealer and was still at the dealer at the time of the complaint. Audi has called in an expert to diagnose the problem. The failure mileage was approximately 46,000. The current mileage is approximately 110,000. The VIN unknown.