they are your stock injectors sent off to a fuel injection company or related company and they basically clean them, hiflow them and test each injector and give you a report.
stock rb25det ones are 370cc, they can be hiflowed to probably around 450cc ish i think ?? unsure of exact cc rating once hiflowed.
i asusme they get the injector nozzle and open it up a bit more so the injector can force more fuel out of its spray nozzle. much like widing the nozzle on a garden hose, more can come out at the same tap pressure.
they dont make any more power at all, it will allow you to inject more fuel into the car once tuned accordingly. its a supporting mod, it doesnt make power by itself