Parallel fuel lines are a great addition to any engine, not only do they provide a more consistent volume of fuel to your injectors but they also yield key safety benefits. With Subaru's standard fuel system design, fuel is fed by a pump from the tank to the front of your car passing through the fuel filter (located in the engine bay) before being fed into the fuel rails. Fuel is then delivered to each cylinder one by one, starting with cylinder four.The fuel pressure regulator (situated at the end of your fuel rails) acts like a flood gate, backing up the fuel pressure to ensure a good supply is available for each cylinder. Experience and logic tells us that a far more efficient way of fueling the engine would be to supply each cylinder with its own equal amount of fuel, ensuring no cylinder is left "thirsty" compared to the rest. This is where a Parallel Fuel Rail design is a far more effective, safe and regulated way of fueling your engine. With RCM's Parallel Fuel Rail Kits fuel exits the fuel filter and is then passed through a Y-piece separator which directs fuel to each rail at the same time. Not only does this solve the problem of one cylinder running lean but it also enables the system to hold more fuel in reserve (thanks to the increased diameter fuel rails and lines). This particular kit is designed for use with modified vehicles where fuel control is paramount to maintaining power and engine safety. Our added Performance Fuel Pressure Regulator will allow maximum fuel control with absolute minimum flow restriction for engines up to and exceeding 1500 HP. Developed with Advanced Bypass Technology and an Enlarged Port Design to provide accurate fuel pressure control across the range, our regulator enables your fuel pump to push more, draw less current, and always meet fuel volume demands with no pressure creep. When fitting this kit we recommend your vehicle is remapped after installation to ensure all ECU fueling parameters are matched.