[Dean]

ABS controller is a seperte controller on the Audi, but you connect to it just like the ECU, and issue commands, etc.

IMHO opinion, if you do a base flush, and then change fluid before each event, the fluid in the ABS controller should be pretty good because it cycles good stuff into the controller when you ABS at the last event. It is unlikely that "bad fluid" makes it all the way from the brakes to the controller and gets in during an event.