do you have the installation manual? as this is covered in it.
you need to check the impedance of the injectors with a multimeter set to the ohms range.
just unplug the injector and touch the probes to the pins
if the reading is above 6ohms(4 a g3 link at least not sure about others)
you dont need ballast resistors. if it is lower than 6 you will require the correct resistors from link