Another 870 thread- Engine vibration

[ZeroNthedark]

Greetings everyone, I'm not terribly good at this so please bear with me.

2005 870 in a 379 dump truck
534,xxx miles
De-mandate of questionable origins (I know, not good, but I didn't do it), was done at 340k miles, bought truck at around 400k miles.
No real major issues until now

The motor seems to have a slight vibration when driving, more pronounced when under a load and worse when engine braking. Has been going on for almost 2 months now, which is making me crazy. Let me backfill the problem for you all:

Early this year I noticed my mileage getting worse, usually around 6, then declining to between 5.5 and 5, depending where I was hauling. I also got a raw fuel smell coming out of the exhaust. Some guys said it smelled like a regen system.

Had talked to Gearhead last year about getting out there, but never made the trip, finally decided it was time. Unfortunately I didn't specify that I wanted him there(too check/fix the programming), so found out too late that he is/was apparently working at home most of the time. Anyway, the other guys there checked it all out- did all the cylinder/injector tests, bubble test( #1 was leaking) and ran the overhead. Now understand that the truck still ran fine, no real loss of power or driving issues that I could tell.

That was May, so I saved a few pennies and made an appointment about a month or two later to get the injector done at a local shop that does Cummins. Had it replaced with OEM Reman and did fuel filters as well. They have done other work for me and no issues, until now. After just a few days, I noticed that the engine had developed a little bit of a miss sometimes, and would run a bit rougher it seemed to me. Saw a good excuse to fire up the Insite to run a few tests and see what I could see. Managed to change something in the cutout test so now it will only do 1 bank at a time, or each cylinder in that bank, instead of each cylinder individually, so now it's worthless for that!

At least it can still read codes, and it showed a 2312- Timing Actuator #1 circuit error. I had bookmarked the post about actuators(http://rawze.com/forums/showthread.php?tid=110) so I pulled them off, cleaned really well, and reinstalled. Ran better, but not great. Grabbed one off a friends 871, cleaned it, installed in #1 slot, and didn't do much. Swapped #1 & #2: Holy crap, it was a whole new truck... For about 2 days. Then back to the same. Removed both, brake kleened really well, reinstalled, ran really well for a day. And that pesky 2312 was back, so I went ahead and replaced both actuators with OEM Remans. Again, ran good for couple days and then crap again.

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The summary is that the truck ran just fine until the injector was changed, then it's been downhill ever since. Well, actually, it went downhill and now it's stayed the same.

I hate taking time off to go on flights of fancy, so that is why I've laid this all out here. My hope is that I can get a solid starting point so that I'm not wasting many days running around fruitlessly and can get some actual results.

So...

-I know the hot sauce is headed my way for that demandate that hasn't gotten fixed properly

-Yes, dampener has been changed

-Does my overhead need re-checked? I don't have the proper tools yet, but am working on it.

-Many threads on here about replacing the various harnesses on the motor. This truck does not lead an easy life, and at 13 yrs old and half-million miles, maybe not the worst idea?

- Could the Reman injector be a dud? Since I can't do diagnostics until a new Insite shows up I'm swimming in the dark.

-Should new Fueling actuators be in my future as well?

-Pretty sure motor and tranny mounts are not in great shape, I have them, just haven't gotten them in yet

Many thanks to anyone who has an idea of where to start. I don't mind being the idiot, as long as someone else can benefit from my idiocy!