Be sure to buy new quality brand injectors. Not the remanufactuted ones.

And adding extra filters will help. First mod I did was add an auxiliary filter and I use the Cummins filters that filter to 2 microns.

Changed at every oil change. The stock filter cartridge looks like a used engine oil filter every time. Diesel fuel sure is dirty crap. And I don't add anything to the fuel... So it's the fuel that's turning the element black.