I own an audi a6 avant 1.9 tdi se 130bhp. I have owned it a year and so far it has been checked for fuel lines blocked or air locked. Vacuum hoses checked for leaks. Fuel filter changed. Maf changed. Ecu tuned. Most days it drives really sluggish with no power, then suddenly the power is unleashed and it goes like hell!! just for a few minutes. It is really strange, normal driving the car is like muted no power no get up and go. and then without warning it goes like stink. What can cause this please anyone? Do I sell it or persivere?