The ultimate fuel system for 500+ horsepower WRX engines - 2 litre - 2.5 litre applications. Purposely designed to be used in conjunction with APS's first stage fuel system and the APS Tumbler Valve Delete Manifold Housing which incorporates the four stock injectors and has provision to add 4 additional Bosch style injectors. By utilizing the stock fuel injectors for low fuel flow demands, the best possible throttle response and drivability is assured - and when high power demands are placed on the engine that are beyond the capability of the stock injectors, the 4 auxiliary injectors are used to provide additional flow and excellent fuel distribution. Billet aluminium fuel rails and Teflon lined stainless steel hoses are part of this high quality comprehensive fuel system. To complete this awesome fuel system, just add a large high volume fuel pump to ensure a reliable fuel supply for up to 700 horsepower. The APS FRP/02 auxiliary fuel system requires mapping through an aftermarket engine management device to ensure precise control of air-fuel ratio to each and every cylinder across the RPM range.