Perhaps the world's most prevalent manufacturer of turbocharged vehicles, automotive giant Volkswagen is a huge backer of the technology, offering it on all their most popular models. VW forced-induction engines are relatively small, produce ample power, and are more economical to run than their larger, normally-aspirated counterparts. Whether you drive a turbo GTI, Golf, Jetta or Passat, the factory power-plant is conservatively tuned and designed with a large margin of safety in mind. A well-executed turbo psi (pounds per square inch) increase by means of a manual boost controller upgrade can tap into hidden performance potential beneath the hood.
Connect one end of the manual controller (there will be two metal barbed ends on the unit perpendicular to each other with an adjustment knob either on top or in the middle), to the turbo outlet source found on the compressor side using vacuum hose.
Attach the other end to the wastegate actuator (located on the turbine section).
Secure the MBC in an easily-accessible area such the radiator mount or lower intercooler pipe for periodic future adjustments.
Turn the controller clockwise to increase turbo boost (counterclockwise will decrease boost), and test setting by obtaining a reading on the boost gauge during a full-throttle acceleration run.
Fine-tune the controller by further adjusting the control knob in the desired direction -- based on psi readings obtained on the gauge -- to achieve optimal boost level (typically a 2-3 psi increase on a stock vehicle).
Add an aftermarket boost and air/fuel gauge to accurately monitor your engine conditions. If possible, have a passenger monitor your boost gauge while you are performing test runs. ECU (electronic control unit) reprogramming will further enhance power gains by optimising fuel and timing maps.
Modifying your engine beyond factory specifications can cause engine damage and void your warranties, so proceed with caution. Use a private road or track for testing.