All of the Common Rail Cummins and Duramaxs feature a relief in the fuel rail which is designed to relieve pressure once it sees roughly 25,000 PSI to avoid damage to the stock injectors. However, most chips and programmers are designed to deliver pressure higher than this, causing the higher pressure fuel to not get to the injectors, losing power, and eventually causing the failure of the stock pressure relief valve.

This simple device will block off the relief valve located on your fuel rail, ensuring that ALL rail pressure is delivered to the injectors, gaining power on the top end. Torque to 70 ft-lbs when installed.