Hi everybody,
First of all, thanks a lot for all the sources, tools and knowledge shared by this forum and its members.
it is an incredible source of knowledge which allowed me to start on the electronic part of my personal project (nothing crazy for now, unfortunately, as I still have to learn many things).
I swapped a 2000 sedan 2.8 V6 (APR) with a totally refurbished 98' 2.7TT AGB engine, and converted the AGB harness to the car.

After many hours spent on the s4Wiki and here, I decided to buy a M-Box from ebay to replace the C-box that came with the 2.7TT.
I dumped ECU and 95040, did the same with the v6 box, and with the V6 cluster (which seems to be a replacement part, with immo 3), to try to make all work together.

I put the maps needed for an EU AGB with a Bosch MAF (pulled from a C-Box dump, and compared it to Mbox already adapted to Bosch MAF), corrected ESKONF, and flash it back to my M-box.
I then tried to start the car, which did nicely, but engine died after a 3s delay... VCDS showed a "18058 - Powertrain Data Bus: Missing Message from Instrument Cluster".
I followed the adaptation instructions provided by Ross Tech for both ECU and cluster, but I can't access channel 50 neither on one nor the other...

I tried the channel 60 adaptation to switch from 0 value to 1025 with no success. (original V6 ECU was with Immo2, according to eepromtool). 
VCDS now shows a 01177 49-00 "No communications", and Motor still dies after 3s.

Using the very handful tools provided by you guys, I managed to take a look into the M-box 95040 (which btw contains a tuner tag "NEFMTO"), and to compare it to the V6 ecu eeprom paired with the cluster, and the cluster eeprom:
- MBox and V6 box has the same SKC, 65535;
- MBox and V6 box has the same Immo ID, XXXXX...XX;
- Mbox and V6 box has the same Cluster code: 00 00 00 00 00 00
- Mbox has a VIN, while V6 box is set to XXXXXX...

So I mixed all of this, and cooked my own 95040: set SKC with the value used in cluster; set the cluster code to the value set in the cluster; changed the VIN to X only and let the immo ID to X only too. EEpromtool was showing "Immobiliser: error, set immo", so I turned it off.

But again, no luck, same messages and engine dies after 3sec...

I'm missing something as I'm a noob, and this time I can't manage to find any clue over the forum or the internet. That's why I'm posting: I need advices from the community on what to try now. 

My goal at the moment is to start the car so that it can drive. I'll have more tune to do later, but I want to get rid of all the little problems before...
For interested people, my project setup for now: entirely refurbished engine, brand new RS4 turbos, A6 allroad plenum, full inox exhaust line, FMIC. Waiting to install my 630cc Siemens injectors and my fuel pump. RS4 B7 rear brakes, and trying to find 8 pots calipers for the front.

Thanks ! and sorry for this long post.

J

Yeah, I know for immo and M-box, but I forgot to mention: I had the same results with a K-box immo off (This k-box is working as I used it on 2 different RS4 B5).
Before the swap, the engine was running perfectly fine.

Eepromtool displayed an error about Immobilizer, that's why I set it to immo-off. But maybe this is a normal status for M-box...
I can flash back "original" 95040 bin with cluster's SKC, VIN, IMMO ID, and cluster code.

I even tried to put back the original V6 box: the car starts and idles almost perfectly.

Another thing: when I try to log in motor module with VCDS, I have some communications problems right after pressing Enter, and I loose connection. I can hear the cluster's relay click in and click out repeatedly, and can't use VCDS anymore. I must turn off and on the car again. (I'm using a FT232R cable with VCDS)

All the flash are done on my bench, and tools provided by the forum (Nefmoto, ME7Check, eepromtool...).
I used Tuner pro and HxD for editing.

This made me check again what I had done with the wiring: I am missing the ECU wire 30 to T32 / 6, I forgot it because I had no idea where it was going when I modified the harness, and the only description I found for it was" Tank warning OBD 2". I wasn't too worried that I didn't wired it, hoping to have a DTC in the worst case.

I'm going to double check the quality of the connection between ecu 43 and T32a/5 too

Edit: I don't really believe in a wiring issue tbh, when I plug the original V6 box, the car starts and idles without any problem... (with missing wire on ecu pin 30). I'll give it a try anyway

Hi, I finally sorted it out, I had to use the CW_CAN_R tweak, has the channel 60 adaptation had no effect.
The car might have originaly been an Immo2 car, the cluster is a replacement one with immo3, so I foolishly believed that with a M box, it would just be plug n' play.

I have some DTCs to take care about, but it starts and idles like a charm. Still have the 01177 49-00 DTC in cluster.