TurboX is 100% correct all GTRs receive the ballast resistor from factory. This resistor is installed to protect the ECUs injector drivers, as they are actually designed for a high impedance injector setup.
You only require one if you have an RB20 and are upgrading to GTR injectors, factory or aftermarket.
Just as a side not I have two sets of fully serviced GTR direct replacement injector sets currently for sale; 550cc and 660cc, both Denso. Details can be found here.