Great info, Gnasher. To clarify:
"Like some Toyota engines, this Audi powerplant family uses both direct and port injection. Direct injection is used to stabilize the idle and in full-load situations, while the port injectors are put to work under partial loads, where Audi engineers say port injection is better at mixing the fuel and air, with less soot produced and reduced CO2 emissions compared to direct injection. Unlike the Toyota setup, this engine operates either as a port-injected engine or a direct-injected one, and never uses both injectors simultaneously."
Reference:
https://blog.caranddriver.com/audi-gives-us-the-skinny-on-its-third-gen-ea888-turbo-four-and-the-sq5s-twin-turbo-diesel-v6/Sounds like once warm, the EA888 runs on MPI injection solely, except under heavy load. So for most people that spells an end to the carbon build up issues of past.