The 6.7L Cummins has a manufacturer flaw on the Fuel Rail Pressure Relief Valve (FRPRV). The FRPRV uses a metal spring to hold pressure on a metal diaphragm. When the fuel pressure gets high enough, the spring depresses, allowing fuel to flow out of the fuel rail and into a fuel return line. Over time, the metal spring becomes weak and starts to prematurely depress. This causes a sudden loss of power and deteriorating fuel mileage. It is most noticeable when the truck is loaded and climbing a grade. Our plug will allow you to completely remove the FRPRV.