ABS faults are very easy to diagnose with a VAGCOM or V-Checker.

My ABS light was flashing when I bought the car and had two ABS related faults. One related to rear wheel sensors. Cleaned the sensors with a compressed air gun and this fault did not return. The second fault was to do with 'pedal position sensor'. I was able to order this sensor for about $120 and fit it to the brake booster myself (a fiddly job, but was done in an hour).

Once this was done, ABS worked perfectly. As usual the Bentley manual came in handy for the remove/refit of the wonky sensor.

I often wonder how many of the VR6 ABS faults I hear about are mis-diagnosed as module or pump issues, when they could just be something simple yet obscure, like the sensor above.