Hi Marcus,
I have a 2003 B6 A4 1.9 TDi Quattro Sport 130 and I have to say that I'm very impressed with it.
I've owned some very quick cars before (Leon Cupra R 225, MG ZS180 etc.) and I was worried that the diesel Audi would be a bit of a letdown with just 128bhp, but I was pleasantly surprised. Its not rapid, but its a punchy unit with a nice surge of torque and doesn't even sound too bad.
The normal FWD model has just 210lb/ft for torque and the heavier quattro model gets 229lb/ft and so that is possibly the one to go for. Of course, the heavier Quattro system dulls acceleration slightly, pushes up the CO2 a bit and lowers MPG a fraction so that is worth considering.
I'm strongly considering a remap sometime in the future but will deffo get the EGR valve bypassed and the turbo and inlet manifold cleaned out first.
I do a mixture of driving and get a whisker under 40mpg out of a tank (510 miles in total) which is pretty good.
Like people have said, regular oil changes with the proper PD oil should see the car run smoothly and reliably.
Hope this is of use.
J