Take a look here:
https://rusefi.com/forum/viewtopic.php?f=2&t=1845Andrey, the founder of rusEFI has a V12 DI BMW he's been running or trying to. I think there are a couple other DI cars they are messing with too. The way it works is interesting projects get support so you have a decent shot at getting help.....but the best path is still probably to map the CAN bus on a running, driving car and start trying to replace signals with an emulator then use that info to run you swap. That is only going to cost you a couple hundred $$, not counting the time of course. You can always fall back to a high price aftermarket ECU if everything it done and you just can't get the stock ECU to work.