Back in the late 70's early 80's there was a water injection experiment....done by GM if I remember right, supposedly was to eliminate carbon build up. when you spray in a little water, the cold water would hit the hot carbon and makes it explode and blow it out the exhaust.

I knew a guy with a Corvette with this on there. Supposedly it got a 10% gain in hp. I dont know how, but thats what he said.
I have sprayed water in my (car) motor to blow out the carbon, but then I followed up with a small dash of tranny fluid to "lube" the 'clean' surfaces after the water treatment. I still dont know if it did any good, but we tried it. The car didnt seem to 'load up' as easy after that.