The systems, for cars, that I have been exposed to were either wet or dry kits. Wet kits use an extra solenoid.valve and a "y" type nozzle. Run a fuel supply from the fuel rail to the "fuel" solenoid/valve, from there to the indirect side of the nozzle. The nitrous runs the same way; from the bottle to the nitrous solenoid/valve, from there to the direct side of the nozzle. There is different sized jets that go between the supply hoses and nozzle, like carb jets, they have different sized holes through them to regulate flow. My system was NOS brand, they have a tech line that you can call for starting points on sizes according to the amount of power you wanted to gain. I adjusted to fuel jet size based on reading from my wide band A/F gauge.