I don think you can adjust the waste gate...you have to get a boost controller.

As for the ALDA, plugging the line will decease performance as the ALDA will think you are constantly running at low boost and will decrease fuel accordingly.

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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