Is it the 92 or 96 that is having the problems?
To eliminate the chance that it is a fuel system related problem I would change both the plastic Primary Filter and the spin on Secondary Filter (if you think the old ones are OK save them for reuse). Next I would disconnect the hose at the Primary filter and run a longer hose to another container of clean diesel fuel (such as a 2 gallons spare gas container). Drive the car a few blocks.
If it runs OK like that you know that the fuel system from the primary filter on up to the injectors is OK. It also means you could be having a problem from the point the hose was disconnected back into the fuel tank (clogged Fuel Tank Strainer or Fuel Tank Vent).

It would also be helpful to know if when you are having the problem is the black smoke, white smoke or any unusual noises and so on.
Dose the transmission have the right amount of fluid in it.

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84 300D, 82 Volvo 244Gl Diesel