One problem related to side/window air bag has been reported for the 1999 Volkswagen GTI. The most recently reported issues are listed below.
Airbag malfunction. This is the 5th time the passenger side, side-air-bag attenuator on my 1999 vw Gti (new Gti) has needed service. First time was just after car went off warranty. Vw regional agreed to pay. About 18 months later, same problem -- had to call vw regional to mount the case for them to pay, and they did. 11 months later, same problem. Dealership paid for repair saying it was covered by their 12mo/12k mile service warranty. 11 months later -- same problem, dealer paid. Now, 5 months later, airbag light on again. Same problem.