You should adjust your Valves.

Has the condition you describe always been there?

At the rear of you intake Manifold is a Banjo Bolt that can get plugged up with crud. If it gets restricted the Boost pressure from your Turbo Charger will not reach the ALDA on the Fuel Injection Pump and the ALDA will not give it the extra Fuel to match the Boost.

Also if you plugged a Vacuum Line into your ALDA instead of the Correct line the ALDA will not work properly.

Also what is your Boost Pressure? Some have had their Waste Gate opening at low pressures and decreasing the Boost Pressure.

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84 300D, 82 Volvo 244Gl Diesel