A friend of mine has an early '99 Passat (2.8l V^, 5-sp automatic) and has a case of what sounds like faulty brake activity.
Specifically, the brakes seem to be actuating by themselves every once in awhile. He says he's noticed it mostly on the expressway - he'll be cruising along, and find that the engine starts to labor (eventually downshifting to maintain speeds >65mph). If he taps the brakes, he finds that their response is unusually touchy. The way to cure it he's found it to stop the car, and then hit the brakes as hard as he can.
Engine trouble and transmission performance don't seem to fit because when this happens, if he gets off the gas or shifts to neutral, the drag is really noticeable. Also, he's been trying to keep his eye on wheel temperature, and has indeed noticed that when this happens, after he's stopped, the wheels are giving off quite a bit of heat (although he said that usually it is the passenger side front that's hot)
At first when I was talking to him, I thought perhaps the brake booster was faulty, but now that I've had some more time to think about it, I'm thinking that his brake fluid is old and either water saturated, or just with an unacceptably low boiling point. It also makes sense that it would happen at highway speeds because any residual drag could warm the calipers up enough to boil the fluid and start this into a thermal runaway condition.
Anyone have this issue with this model/year in particular? I haven't heard anything about failing boosters...
Thanks, Arthur