1984 300D- Rough Idle

[Noah300D]

Hello everyone, I am new to the Mercedes diesel world. I am familiar with mechanical diesel, but this car is making me scratch my head a bit. I've owned my 1984 300D for about 2 months now, and its had an off and on rough idle/reduced power. So far, I've cleaned the fuel tank, replaced the strainer in the fuel tank, new rubber fuel lines, rebuilt lift pump and fuel filters. I have also lashed the valves back to factory specs. The car has had a bit of a fuel cleanliness problem- was very dark in color and murky when I first drained the fuel tank. Knowing this, I've added some biocide to the tank, and have been changing the filters out pretty frequently. Usually, changing the filters out is enough to get it running great again. However, this last time hasn't seemed to make much difference. The engine is shaking like a paint shaker, and is much louder than it was a week or so ago. She has 158,000 miles on her, and doesn't smoke at all- unless its very cold out. Any help or guidance would be great! Thanks in advance.