Just had fuel injector replaced in November and 3 months later the car is having similar symptoms. Intermittently stuttering or misfiring. Audi mechanics kept car for the weekend and replied they couldn't find the issue and that they thought it may be out of fuel. I assured them the vehicle had approx 1/4 tank when problem arose intermittently, and they wanted to return the vehicle to me without finding the issue. They kept the vehicle again and finally had the problem return for them as it reached approx 1/8th tank. Still couldn't diagnose the problem but concluded that it was a fuel level sensor and that the car was out of fuel when showing 1/8th tank even though I advised that I continued to drive the car for about 100km after having the issue when I brought it in!! Frustrated!