An interesting observation I wanted to bring up in this thread: The reason why no one with a tune (JBD, Evolve, etc.) posted issues with carbon build up, etc.
The best way I can explain this is:
All tunes for diesels = More Fuel Volume
More Fuel Volume = More Air Necessary
In the M57, More Air is controlled by giving LESS EGR (hence more Oxygen).
LESS EGR = Less soot and less carbon