I've got an A4 B8 2.0 TDI 143 SE. Had it for a while and I have been recently looking at getting an A5 Quattro, but have decided against and I think it'd rather spend some money on the car as it is!
The car is used daily for work so keeping/increasing fuel economy will be big factor in whatever I change! A few friends had suggested a remap and something like a Milltek exhaust system.
All the best.