Despite being a performance-geared enthusiast vehicle, the Volkswagen GTI has never been equipped with a turbo boost gauge in stock form. Boost gauges allow you to monitor a turbocharger's PSI output in real time. This is valuable in diagnosing problems such as vacuum leaks or turbocharger damage, as the driver is given a numerical readout of turbo activity. Modified GTIs are especially in need of a boost gauge, as numerous stock components are more likely to fail under the increased boost of even just an ECU reflash. Installing a boost gauge in your MKV GTI will allow you to ensure your turbo system's efficiency, and it can also add an attractive touch to the interior of your Volkswagen.
Remove the plastic engine cover overtop of your MKV GTI's engine by removing the Torx screws that fasten it to the engine head. Look along the right side of the engine near the intake manifold for a rubber cap held in place by a clamp ring. Remove the clamp ring and rubber cap, exposing the metal bung beneath.
Install the T-fitting supplied in your boost gauge kit onto the exposed bung by sliding the T-fitting's side opening over the bung. Be sure you force the T-fitting down hard enough to achieve an airtight connection.
Connect your boost gauge's vacuum line into the bottom opening of the T-fitting. Route the under end of this line to the boost kit's sender unit, and connect the line onto its designated bung. Mount the sender unit somewhere remote, such as on the washer bottle flange, by securing it with zip ties.
Route the boost gauge's vacuum line into the engine bay, from the interior of your GTI. This can be done through any of the stock wiring holes in the firewall, such as of the ECU wiring harness near the driver's side floor. Plug the vacuum line's end into its designated connection on the sender unit.
Secure your boost gauge in a gauge pod by placing the gauge inside and tightening the pod's face. Mount the gauge pod in a desired location with supplied double-sided tape and/or screws.
Remove the plastic interior panels around the stock gauge cluster. Route the boost gauge vacuum line up through the dash area and connect it to the rear of the boost gauge. Feed all excess lining into the dash area and secure with zip ties.
Wire your boost gauge's lighting to a power source, such as the wiring for the stock dash light wiring. Strip about 10 millimetres of isolation from one of these wires, and splice in the boost gauge power wire by wrapping its end around the exposed stock wire and securing the connection with electrical tape.
Secure all excess wiring into the dash area with zip ties. Replace all plastic interior panels by the opposite procedure of removal. Likewise replace the plastic engine cover.
Start your MKV GTI to ensure your new boost gauge is fully operational. It should display vacuum pressure at idle and boost pressure under acceleration. An unmodified MKV GTI should produce a peak boost of roughly 14 psi around 3,500rpm, slowly falling to about 8 psi by redline.