Its not the diesel fuel that kills them, the HEUI injector design was a piss poor design from the get-go. On bigger engines, they worked better, such as the 7.3, the injector in and of itself is much larger, in comparison to a 6.0 injector. Fuel injectors are lubricated by obviously the fuel flowing thru them, and also cooled at the same time. If your fuel pressure drops below 40 PSI on a powerstroke injector, it will literally eat itself. The plunger in the tip of the injector heats up and then somewhat melts itself to the tip body. This causes the injector to stick open, creating a rough running, hard start, a constant blue haze when cold, and leads to burning a hole in the top of the piston which gets into costly repairs. Another failure on these injectors is the spool valve, which is due to crummy oil, make sure you change your oil regularly! I have gotten in the habit of changing my oil every 5000 reguardless. I always run a synthetic oil, it is very important to keep good oil with a constant viscosity in your powerstroke HEUI injected engine. As for the turbo, the VGT design is a great idea, but International's design had some flaws. We offer upgraded turbos from stock to wild, which all incorporate a 360 degree thrust bearing rather than a 270 degree bearing which is what is stock, and tend to stick the vanes. Make sure you keep your EGR valve clean as well, and consider doing an EGR cooler delete, which will improve mileage, power, and get rid of any problems you may have had with your EGR cooler in the past and future. Hope this helps! Glad you got a new 6.4, your mileage may not be satisfactory for a while, til you get it broke in, and/or do a DPF delete kit. Call me if you have any questions! I'd be happy to answer any questions!
~Steel