As I mentioned in another thread, my car is still at the dealership. They are replacing the complete engine harness. I'd be damned if this is the source for all the injector, DDE, electronic failures...They should be done with the repair end of this week, lets see how it goes.
This diagnosis came from the Regional BMW Engineer. It is a very laborious job from what I understand. I would think to authorize such an expensive repair requires some "proper diagnosis".
From what I know, I would be the first 335d (reported on forums) to have the engine harness repair.
Regarding the carbon build up/soot build up, the new EGR valve + cooler should help; I would still consider a tune. Remember, Tune = More fuel = Less EGR = Less soot, less carbon; (the M57 has a lot of potential, but of course to meet clean diesel standards, BMW had to turn down the power to meet emissions standards).
Meanwhile, I am enjoying the 2013 328xi. Great car, but would never consider it over the 335d. Now that I have tasted the 335d, I am unable to size up any other car that is comparable.