If your Turbo has the Rubber Hose going from the Intake Manifold to the Waste Gate some people have installed a inexpensive manual boost controller valve as sold on eBay for around $10.
You adjust the spring loaded valve so that the valve will not open until the manifold pressure you want is reached.
When the Valve opens your Wastgate gets the Manifold Pressure.

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84 300D, 82 Volvo 244Gl Diesel