These boost controllers are simple to install with your performance upgrades and aim to reduce the pressure seen by the boost actuator that opens the wastegate.  

There are two ways of doing this:

1. Put a spring loaded restrictor that can have the pressure on the spring adjusted.  More pressure is required to overcome this spring before the diaphragm in the actuator can be pressed down. This is like the Turbosmart design.

2. A T is installed in the line between the boost source and the actuator.  A restrictor is placed on the boost source side of the T and air is bled out of the  side going to the actuator.  This system has no moving parts and allows the adjustable needle valve to be placed in a convenient location.

We've tried various brands and configurations over the years and have found an off the shelf setup that works great (after the few tweaks we have done) and ensured it is correctly installed.

Boost controllers are normally setup during tuning to get the optimal air fuel ratio under boost and then should be locked so they don't move. These units have a grub screw to do that.

These are sold as kits with the items shown, clamps and silicon hose in two sizes to connect to the turbo and then for remote mounting.