No bias valve on the 16v. It's all run by the abs unit which may be why you have a problem.
I would suspect you have a speed sensor fault on one of the wheels.
Paul
True, but only on later models.
I'm sure the early models, like the 8v and vr6 still have the valve. I think it changed about 1995?
If the abs system has shut down then there is a potential for the back brakes to lock, as Paul said, that model doesn't have the bias valve.
Put the car on VAG com, or test all the sensors for continuity, duff sensors usually won't give a reading at all.