Hi! Im wondering whether this issue is a reason my audi is currently poorly! I have an A4 Avant - engine light is turning on and off, wont accelerate - then will work perfectly fine. RAC sad it was a NOx sensor, where-as an audi specialist said it was the AD Blue tank and that needs replacing. Car is booked in with Audi for an investigation, but on booking they said the car had an engine software recall. Could this be the issue/same thing?