I purchased a 2000 A4 1.8t quattro with apr stage 3. The previous owner had replaced the motor, he said it was a rebuilt motor from audi. I need to get a rear oxygen sensor so I checked for the engine code but the tab is blank. In not sure if I should get the sensor for the AEB or ATW motor, or it might not matter since it has the apr ecu. If not knowing the engine code is going to cause many part ordering problems in the future is there a way I can find out what motor I have? Thanks for your help