"I will have to replace all the 4 injector return lines (#1) and the diesel cigar hose (return fuel line #8) because they are not the proper hoses, right?"
If it ain't broke don't fix it. I just pointed out points of interest about the items you listed. I have used bulk hose for the fuel return many times. I have never heard the noise that the hose is designed to reduce. Others have heard it though.
Bosch Master, ASE Master, L1
33 years MB technician