Yep......diesel injectors seem to always have issues too. The 6.0 in my F250 uses the HEUI type injectors that actually operates off of high pressure oil. Dirty oil, and low fuel pressure it what eats those injectors up. At least the diesel injectors are somewhat affordable if you have to replace them, not like the $400+ each N54 index 12 injectors.
To comment on your post, from what I've seen, and after talking to a few of the big injector shops that "attempt" to service these N54 injectors, it seems the main issue with them is that they are piezo type injectors...simple as that. Not sure if you are familiar with how they work, but basically, they pass an electric current through a stack of piezo crystals to get them to expand, and that opens the needle inside the injector to meter the correct amount of fuel. Over time, the crystal degrade, swell up, and don't respond properly to the electric current...causing all kinds of lean and/or rich conditions with fueling.
And, unfortunately, from what all the injector places have told me, there isn't a single shop that has the ability to recharge/restore the piezo crystal stacks. I think the Injector shop says they can "restore" the crystal stack, but it sounds like it's basically just cleaning things. And even after that, if they can't hit the proper flow rate on the injectors...they are trash.
It's just a finicky, expensive to manufacture, and an extremely complicated design for an injector. That's why BMW went with solenoid type injectors on motors like the B58...and ditched the piezo injectors. I think all their diesel motors use solenoid type injectors now also..but I could be wrong.
And then take into account that these N54 engines have been out for 16+ years....so there are lots of older (and fake) injectors floating around out there.
I wish someone would come out with an affordable aftermarket injector that would be plug-n-play...but I doubt that will ever happen.
But to your point....YES, I'm sure dirty fuel cause issues with the injectors. There isn't much of a fuel filter setup on these cars. A small filter on the LPFP, and a small little screen on the HPFP. No big pleated fuel filter like on most cars and trucks.
Lots of great info here ......
https://theinjectorshop.com/blogs/news/bmw-piezo-injector-service-faqs
https://injector-rehab.com/knowledg...ons-for-piezoelectric-fuel-injector-cleaning/