Most modern fuel injected vehicles run a fuel pump in the tank and run much more fuel than it is needed to the fuel rail. A regulator keeps a certain amount of fuel pressure in the rail and then sends the rest back to the tank. However, tuners upgrade the air intake system as well as the exhaust system and often neglect that more fuel is needed to make those mods perform at their full potential. This Fuel Pressure Regulator is adjustable so you can tune the fuel pressure to your needs.