Nitrometano

I have an Electromotive Tec2 and I'm using the stock 550cc fuel injectors in my S5 engine. Right know they are wired that 4 injectors work at the same time. I want to have a staged injectors like the factory system works. In that manner I can use the 500cc primary injectors and then add a secondary bigger injectors to supply the fuel that the engine needs. I know that the TEC2 and the Wintec2 program version 2.1.2 have a few features on the GPO output. What feature I need to choose (or if there is another way) to trigger this secondary injectors?