That is exactly where the debate is. The claim is that the 6.0 banjos starve the rear most injectors and that the 6.4 banjos do not due to the larger bore and the removal of the check valve. That is, basically the debate is whether the 6.4 banjos enhance the flow of fuel to the injectors or not. So far I haven't seen any negative comments on them, but I also haven't seen any concrete evidence that they are needed. As far as I have seen, once the fuel spring is upgraded the 6.0 banjos perform their job at providing sufficient fuel to ALL the injectors, including the rear most injectors.Well I would say they can't hurt and only help with the fuel flow to the injectors. I've spent money on worse mods.