What number of engine control unit I have to look ?
Is it important to look for engine identifier (BMJ / BDB) or transmission ( manual / dsg ) ?
Well, you need similar ECU hardware, not just the CPU. Ideally you would want a ECU from 100% identical car, everything else requires additional research.
I'm not 100% sure about this particular car, but usually ECU hardware for different transmissions is identical, meaning the software is cross-flashable. You can check for Bosch number on the spare ECU (026...) - if it matches, it usually means that you can replace yours with it.
As a wild guess - any 3.2 VAG from that era with ME7.1.1 should work, but don't quote me on that. Double-check with someone else.
