I also own an 02 passat turbo (same motor as your A4) the bypass valves do have a problem with leaking, mine just turned 60k, as luck would have it, the turbo crapped the bed, making a loud tapping sound when boosting, also due for a t-belt, plug change, clutch is going, and front brakes are low. WEE have I got a fun filled time ahead of me!!!
[I]"Winners never quit, quitters never win, those that never win or quit are idiots."[/I]