[Kraftwerk]

I bought a '94 960 D24TIC2 a year and a half ago with dead engine. Rebuilt it ground-up, and made less than 15k miles since.

It ran like a dream, started warm or cold with no cranking, never smoked, just like it was supposed to, until about a month ago.

Then, strange things start happening: First, there was some rattle under the hood, which I supposed to be loose alternator belt, but it didn't go away after tightening it.
Somewhere around that time, it would still start at first crank in the morning (naturally, I always wait for the glow plugs light to go out, then crank it) but it would sound like it's working some 200-ish rpm below normal idle. Tacho is broken, so I can't be sure. Also, the whole car would shake as the engine would work really rough untill normal working temperature is reached. Then, problems usually stop, except for that rattling noise (tak-tak-tak-tak...goes faster/louder as I rev the engine up, and vice versa). If I'd start driving immediately after firing it up, it would jerk forward every couple of meters, on low revs. As if clutch would slip and then grasp tightly...I was told that might be due to injectors.
Also, it smoked like a wildfire.
I went to my mechanic, he said that VE pump "moved" somehow, and therefore ignition was off...I left the car overnight there, and in the morning he unscrewed it a bit, I started the engine and he tilted the pump left-right until smoking and shaking completely stopped. Then he tightened screws and I drove off. Everything worked like a charm again for some 7-10 days (except the rattling was still there) but then it all started coming back.
Now it takes longer to warm up, it shakes really roughly while cold, smokes EVEN MORE (if possible...makes smoke granade look like a joke) untill warm (then there is no more visible smoke, as if everything is fine) sounds a bit different all the time, I think I feel slight lack of power, but when I floor it, it does quite a nice burnout, no torque loss there.

Worth mentioning is that at one moment it lacked 2 liters of oil out of the blue...I filled it up straight away, and it hasn't used a drop of oil since.
It doesn't lose water and there is no oil in water expansion container, no blue smoke as well, so I would rule out piston rings, blown head gasket or cracked head. I guess worth mentioning is that it never overheated, actually, the temperature never went up more than half the scale (which is normal working temperature).


So...my lucky guess would be something related to Bosch VE pump or injectors...but I have no specific clue.

Anyone?

Thanks a lot in advance and sorry for such a long post.