a flashing check engine light means the car is misfiring. driving like this can cause cat damage! vw and audi have recalls for defective ignition coils which are responsable for over 90% of all misfires on these cars. take it to the dealer, if its coils the repair (including diagnostics) is FREE
Search for "Check Engine Light" on the Encyclopedia (http://repairpal.com/encyclopedia) If the Check Engine Light flashes is a warning that the engine computer has detected a misfiring and that will damage another components of the emission-control system. Have your vehicle inspected as soon as possible.