I've done some research into this area as well because I also own a RG500 Gamma. A guy named Randy Norian has done a number of mods to his RG500 which includes water injection. He does an excellent job of explaining what it does.

Here is the link:

http://homepage.mac.com/rg500delta/deltaphasetwo/

Go to the bottom of the menu and click on water injection.

To do this properly you need to know when to start the mist of water in relation to the power valves opening/closing. I'm not exactly sure but I believe you don't actually gain horsepower but the peak torque just hits earlier.

I thought about doing it on my RG500 but I don't like the idea of having sludge buildup in my pipes caused by the water.

Only problem I can see with doing it on a NSR is you may need to alter the powervalve opening and closing range depending on the pipes you use. On the RG500 there is a box modification that will allow us to alter the powervalve operation. Not sure if you can do this on an NSR. The other problem I can possibly see is the powervalve must be open and closed completely for it to work properly. I think the NSR has a progressive powervalve...not sure.

Imagine, you can have a button that turns on the water injection when needed to change the torque characteristics. That would be cool