Audi 90 Quattro 1990, California Edition

[Olli]

If you wonder, my car has spent its early years in California - which is 
hardly the cause of its brake problems. I have 2 inter-related questions:
1. As I am looking for a Master Brake Cylinder, would anybody have a 
suitable specimen?
2. The questions I get, when trying to find a replacement, is whether 
the braking system is working on vacuum or hydraulic servo. as a 
non-technical person i do not know the answer. Advice appreciated. Olli