Weak spring in the wastegate will degrade the turbo boost in two ways. One is slow build up of the boost pressure. Another is lowered maximum boost pressure. Hook up a boost pressure gage and you can observe the current state of the wastegate. There is a boost pressure vs RPM curve at maximum load shown at the 123CD. It shoots straight up near max boost at 2K RPM at maximum load.

My 83SD was getting max boost around 8.5 psi and boost pressure build-up is slow. I think the wastegate "leak" some pressure so that the build-up is slow. There is also some "roughness" perhaps due to the modulation of the leaking boost pressure.

Out of curiousity, I clamped the wategate hose. The boost came up much faster and the maximum boost pressure is around 15 psi. This totally changed the dynamics of the car.

Rather than fooling around with the wategate spring (a PITA job for the Garret), I made a pressure regulator using a vaccum/pressure relief valve (part#48935, MacMaster-Carr) and some brass fittings out of Home Depot. Now I can dial in the desired maximum boost pressure while getting a fast boost pressure build up. Total cost less than $20.

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Shane83SD