I have a '99 A6 ARS 4.2 with a bad cluster, it's a Jaeger/Magneti Marelli unit with a broken FIS display and all the little dials showing wrong readings. This is a IMMO2 cluster.

Then I have a spare parts car. It's a '00 A6 ARS 4.2 with a fully working VDO cluster. This cluster is IMMO3.

I already corrected the mileage on the "new" cluster and swapped it to the "old" car. I don't care much for immo so I disabled it from the '99 ecu with bootmode and immodef binary. Now the car starts fine but the immo light keeps blinking on the cluster. I'm thinking of enabling immo if that is needed for the light to go out. I figure I have a couple of options.

1. Just write the eeprom contents from the spare (IMMO3) ecu to the old (IMMO2) ecu. Not sure this will work and definitely sure won't try it before someone can confirm that it won't brick the ecu beyond recovery.

2. Grab the ecu from the spare parts car and use that with the spare ecu, I also have the keyfobs so no biggie. Just need to adapt the remotes.

3. Make the necessary modifications to "new" cluster eeprom and "old" ecu eeprom. Now this is the option I'd like the most. I already have ecu and cluster binarys read and I could make the necessary changes but before I go any further, is it possible to marry IMMO2 ecu and IMMO3 cluster?

The other option is to remove the led for immo from the cluster mainboard or use masking tape to cover the light