Sorry to hear of your problems. I usually use Cummins, but have found that their service is only as good as their assigned technician. If he can't find it, he punts. With one exception, I haven't seen them get help from a more qualified person or the manufacturer.
I did find a very good trucks electrician that was able to properly solve my exhaust brake's electrical issue, as well as a gremlin in the toad wiring. But, Long Beach, California is a bit of a trip for you. I'm certain a good electrician, with truck experience, could find it for you.
2003 Alpine 40FDTS (400HP)
Long Beach, CA