Today I fitted a tuned n75 valve sensor which I bought from a German company I took it for a spin and it seemed to have sorted my problem out but tonight taking my son to a class I was driving along it was just about to boost and then blurrrr and the epc light came on the dash and the car just wouldn't go . I pulled over and turned the car off took the key out and then restarted it and everything was fine but in the owners book it say if this light displays take it to the audi shop without delay ! It seems fine now but should I be worried help please