When the injectors and fuel pump are upgraded to a larger flow setup the stock fuel pressure regulator will not be enough to suit the required pressures for the new setup. Also the stock is already preset to from factory for the standard setup and non adjustable so it will be restricting the tuning potential of the car. The TOMEI Fuel Pressure Regulator will ensure stable pressures are supplied with the oversized diaphragm. This special design has proven to maintain the required pressure levels with any adjustments made