I would say a 2003 , because then 1) you do not have PD engine, with its special oild requirements, 2) your VAG-COM software package can work this this engine
2a) recommend rest autotrans to the european seting- better shift points, 2b) reduce the EGR duty cycle 3) This non PD engine has computerized mechanical timing pump and individual injectors 4) this model 2003, has the 80K or 100K miles timing belt and pulleys setup OEM ( my 2000 has the 40K-50K one) 5) this engine can use Amsoil series 3000 5w-30 diesel engine oil or a lot of the popular synthentic oils as long as they meet the specification, which is easier then the special PD oil .... the 2004 on up is the PD engines, the 2000, maybe 2001 was the
40K ( can stretch it to 45K ) timing belt change requirement. IF you do get a used one that need timing belt, then have them pull and clean the intake manifold, replace the MAF sensor, replace the water pump and thermostat, replace the EGR valve, and clean out the intercooler. Seems like a lot but you will are quickly eliminating maintenance points. Also check the glow plugs and GLOW plug HARNESS...... Install ProVent 2000 CCV filter to catch the oily blowby. Good Luck