Cedric,
I think you will find the correct tool is expensive, I'll have a dig and see if I can find one, I have a few. But to be honest for the sake of 6 injector connectors, I would probably just manual crimp and solder if it were me
. Done properly they will be fine and handle the current no issue... You can do it without causing a latent fatigue point provided you don't hold heat and flow solder too long (use a nice hot iron, and you will be able to solder faster) and thus not allow it to wick up the wire.
Martin