I have also Audi 80 1.9 TDI.It was in a very good condition,and is still working very well, during 2 years of using it we had no problems with the car.The engine works very well and is really very economic.Also very importatnt thing is that it doesn`t lose too much value after years..I think,two wires going to one of the injector.So,first you will check injector.