Change to a different brand/type of gas (4-5 tanks) VW had a bulletin out on this. They recommend Shell, Chevron & AMOCO(?
• Use a good Fuel Injector Cleaner every 4000 miles. See Chemicals for recommendations. • Use fuel dryer (using ISOPROPANOL NOT Methanol) • Check (idle) throttle switch • Clean sensor plate or airmass sensor & throttle body orifices • Change the fuel filter • Clean idle stabilizer VALVE with brake or carb cleaner (VW&P) (Note: Earlier cars had a Digital Idle Stabilizer circuitry (DIS) which is something different, and *rarely* fails).