One problem related to power assist brake vacuum has been reported for the 1998 Audi A6. The most recently reported issues are listed below.
Manufacturer's recall # ku brake booster and NHTSA recall( 99v248000),tie rods. Contacted manufacturer on October 12th. Dealer had no parts available for brake booster and tie rod recalls. This could result in a crash. After numerous calls to dealer's maintenance department to schedule service, consumer could not be told when parts would be available. Service department was informed that the vehicle was driven in temperatures mentioned in recall.