Distributor failure?
 

How many people had the hall sensor in the distributor fail?

If your Audi starts to intermittently misfire or completely die but only to restart after a short period of time, then the Hall sensor is probably on its way out. It took me two tows to finally nail this one. My '91 1CQ ECU didn't display any codes since there aren't any codes for a bad or missing hall sensor signal. A quick test is to remove the distributor cap and give a shot of "Quick Freeze." If the car restarts, problem solved.