Like Mark said, they are front wheel drive. The engine is mounted longitudinally rather than transverse, so there are differences with the Golf/Jetta arrangement. The manifolds are different, and they had 1 or 2 hp less than the turbodiesel Jettas and Golfs. The car is heavier too.
There's not a lot of performance suspension stuff for the Quantum (B platform), but any suspension for the Audi 4000 FWD cars will usually work on the Quantum as well.
Basically, follow the same ideas you use on a Golf or Jetta. Diesels like lighter weight wheels and tires, and less weight anywhere else you can make things lighter. A big exhaust will help the turbo spool up better. Wastegate mods and an intercooler will help with power. Watch exhaust gas temps, and keep the fuel flowing for more power.
I think the rear axle beam is the same as on the A2 platform. I'm not 100% sure, though. If it is, then a GTI rear axle beam with the thicker stabilizer bar would help, too.