It could be an Air leak somewhere. Does you model have a Fuel Heater?

Are you using only Diesel Fuel?

Try running with out the Fuel Fill Cap off.

I have not read of anyone using the Bozio injector nozzles on your year and model until now.
You might hook up your Fuel Lines as if you were going to do a Diesel Purge but run it on Diesel first. If it runs better that could indicate you have an Air leak towards the rear of where you disconnected the Fuel Hose.
If there is no improvement from above since you partially set up for it you might do a Diesel Purge. If that cures it was the Injectors.

There has been a few members who had issues with their Fuel Supply/Lift Pumps. I did not pay attention to the Symptoms when I read there posts.

Some members believe that it is possible for the IP O-rings to go bad and allow Air in but not have an external leak.
Perhaps removing the Delivery Valve Holder clamp (M pumps only) and squirting some thick Oil around the base of the Delivery Valve Holders would temp seal of any Air leak if there is one. This also might work to see if there is Air leaks at any of the other Fuel Line connections on the suction side of he fuel Supply system.

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84 300D, 82 Volvo 244Gl Diesel