I am using a standard wastegate actuator like the one forced posted in conjunction with a vacuum actuator hooked to the VCV for the transmission. The wastegate (pressure) actuator alone will work, but it will likely just cause the turbo to put out a set pressure, even when you don't need it (partial "throttle", cruising etc)

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1979 240D- 316K miles - VGT Turbo, Intercooler, Stick Shift, Many Other Mods - Daily Driver

1982 300SD - 232K miles - Wife's Daily Driver

1986 560SL - Wife's red speed machine