yes the ecu in the subies are very good but I've never seen any cars ecu that will compensate for highr flow injectors because higher flow injectors will supply more fuel at every rpm range your cars stock ecu is programed to run a certain size injector. The SAFC 2 will control the fuel amount easly with no problems with running rich. remember scott all stand alone ecus require you to tell it what size injectors you will be using so it knows what the flow will be and calculate for it once you have you base map done same with a stock ecu at the factory. here is a link for where I read about the fuel delivery mod for turbo rs cars.
http://www.ravensblade-impreza.com/