Your Subaru fuel system includes the fuel pump, fuel injectors, and other important bits like the fuel pressure regulator and fuel rails. These parts work together to delivery the proper amount of fuel to your Subaru engine. If you increase the demand for fuel -- by running more turbo boost, for example, you may need to increase the supply of fuel. Note, though, that if you already have enough fuel capacity, adding larger fuel injectors or a larger fuel pump will NOT increase power in any way.

Also note that the ECU is not able to sense what size fuel injectors have been installed. if you upgrade the injectors to a larger size, you have to tell the ECU using custom ECU tuning.