An even easier way to accomplish the same thing is to put a boost controller into the air pressure line to the wastegate actuator. One additional benefit of doing it this way is that instead of a single, static setting for the wastegate actuator (like you get from adjusting the spring tension) you get an easily adjustable setting. This makes it easier to fine-tune and get just the turbo boost pressure you want/need for the amount of fuel your IP and injectors are supplying.

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1984 300 Coupe TurboDiesel
Silver blue paint over navy blue interior
2nd owner & 2nd engine in an otherwise
99% original unmolested car
~210k miles on the clock

1986 Ford F250 4x4 Supercab
Charcoal & blue two tone paint over burgundy interior
Banks turbo, DRW, ZF-5 & SMF conversion
152k on the clock - actual mileage unknown