PFC's can't adjust for different impedances, so yes you'll need to add some sort of resistor. A GTR pack will work or you could wire in a resistor in series to each injector. 10W, 10 Ohm resistors seem to work well.
Just checking, but you are aware that RB26 injectors are top feed while RB25 fuel rails only accept side feed? You running a modded fuel rail?