I run alky/water in my car and i spray it after the turbo, now im not that knowledgeable about supercharges but the same ideas apply, now is a roots the style that sits right on top of the intake correct? Now if this is the case its a pain in the ass to inject water unless you can put a spacer with a nozzle or just tap right into the small plenum you may have under the supercharger. As for injecting before, you can but i dont know what it would do to the supercharger, on turbo cars if you inject before the turbo it will eat up the turbo but the turbo is also spinning way faster then the super charger does.my guess it would be ok as long as you didnt do a large amount. But i would sugest figuring a way for the injection to be done after the charger since you want it to evaporate right away and not have the possiblity of water puddling in the charger if you spray too much before. Hope this helps.