The vehicle ran fine until it started going into limp mode upon normal acceleration, then had to turn key off then start again to reset, I had the car taken to two different Audi dealerships and the last one in Appleton, WI was the worst, they kept the car 11 months, tried all kinds of things but nothing worked until I took the car back, limped it back home. Took it to a local garage, and they figured it out. Changed both diesel particulate filters and the problem was solved. I suspect it was an issue with the def, because now I am going through a lot of it, and may have contributed to the problem.