Shimming the wastegate on a MkIII Supra is a cheap and easy way of gaining extra boost. It is not adjustable like the other methods of increasing boost pressure so you won't be able to tune boost levels to match atmospheric or driving conditions.

To shim the wastegate, remove the air hose going from the intercooler to the 3000 pipe. Then remove the two bolts holding the wastegate actuator on , put two washers (or more for more boost) on these bolts and replace the bolts. If yuo use more than two washers, you may have to get longer bolts.

This picture shows one of the mounting bolts (on Jonas Nylin's MkIII). There is another one identical to this on the other side.