It appears that the fuel injector + DDE failures are not related to the carbon build up issues in our 335D.
My 2010 D first had a fuel injector failure which was replaced.
But after driving for 30 miles the CEL reappeared and it went back to the dealer.
This time the dealer discovered carbon build up so the intake manifold was replaced and the cylinder head was cleaned off carbon build up.
I drove another 30 miles and the CEL came back.
I told my dealer that other Ds had to have the DDE replaced to fixed the CEL and provided print outs of forum posts.
This time BMW agreed to replace the DDE.
Since then the CEL never reappeared.
I was told to expect carbon build up in another 50~60,000 miles!
My D was not covered by warranty as the issues happened at 65,000 miles.
The total costs was over $13,000.00.
At my request my dealer worked with BMW and out of good will BMW covered over $9,000.00 of the costs while I paid $3,800.00.
I drove my D for over 3,000 miles without further incident.
But I wasn't comfortable that the D will be trouble free from here on so I traded it in for a 2013 E350 BlueTec.
For the E350 BlueTec I started using
AMSOIL Diesel Injector Clean additive in the hope to avoid carbon build up issues.