Kye, you should run water to the stinger cone but put a restrictor on it . like a flow control valve. as far as injecting into the head pipe chamber it is hard to see where the injection points are. i see the MID capped off. if you could tap in or introduce water right after the manifold or coupler i think that may be ideal. but if you only have the top nipple avail. start there. you can restrict that flow in there too. utilzing a control valve or a restrictor valve. you could also look into the MSD injector nozzle probes they use on the water injection systems. Then you could drill into the pipe and set it where it beneft the most. You want to dry that pipe out as much as possible without getting to the melting point of couplers or manifold damage. some guys run bpipes and only introduce the water at the stinger into the waterbox. leaving there screws closed to keep the pipe dry but this is done with caution and usually much cooler water temps. If you are single cooling you can tee it off to dump most water overboard and use whats after the tee for the pipe stinger or injection. if your running dual cooling you will want to dump one line off the engine or head over and use the other for the pipe. just dont have both lines feeding the pipe.
-if it were me, I would cap the top and the mid. and start SLOW at the stinger and see what performance it yields and check on engine and pipe temps. then if it is too hot or marginal, then I take step 2 to the top nipple and run a restictor on there one that is adjusable and crack it a pinch. let the water in, check temp and rpm response.. leave it where the power is avail but not water bogged down.
