Ok, so got the car back. Under warranty the following items were replaced:
Cyl 4 injector
High Pressure Fuel Pump
No signs of carbon build up in the car; Good News for me.
BMW thinks maybe possibly at one point some gas was mixed with the diesel fuel in the past. This could have been the culprit for these injectors to fail. They did not have ANY OTHER explanation after 1 month of having the car with BMW NA involved. Inspection of the gas tank did not show any signs of gas/diesel mixture, but they did find small "metal particles" in the fuel rail, not sure from where. Maybe the pump...
I hope some gas stations are not mixing gas and/or kerosene with the diesel fuel to "cheap out" or "winterize"...
Feels good to have the car back. Seems to be running OK.