Direct port nitrous oxide systems use the same setup again as the others apart from the engine side of the system, it is activated and the bottle feed is installed in exactly the same way, even the solenoids. The only difference is the injection method to the engine. When the solenoids are activated the nitrous oxide and fuel still flows out but it takes a alternative route to other systems. Most other systems inject the nitrous oxide and fuel into the air intake manifold. The direct port system injects the nitous oxide and additional fuel into the branch intake manifold. So where the other systems using single point injection will only use one injector nozzle to inject the nitrous oxide and additional fuel, the direct port will use four as one needs to be placed on each branch of the manifold. This is a more complicated setup for nitrous oxide as more complex and time consuming modifications to the manifold must be made. 4 holes approx 8mm need to be drilled into the manifold (one on each branch) for the injector nozzles to be installed. The holes either need to be tapped or have a bung welded above the hole to act as a spacer depending on the internal bore of the manifold branches and also the depth of the nitrous nozzle. The bungs would need to be tapped so that the nozzles can then be screwed into the manifold. *A bung is basically a nut welded above the holes on the manifold to allow the nozzle to screw into.