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 a un-modified vehicle where maintaining engine safety is the primary goal. Supplied with a conversion bracket to connect your standard fuel pressure regulator the car does not require any form of mapping or manual tuning after installation. If your vehicle is modified to increase power then we suggest our Parallel Fuel Rail Kit with our Performance Fuel Regulator which will allow complete control over fuel pressures where a greater volume of fuel will be required.