I know of one person on another board who ran KB pistons with nitrous. Supposedly his carb got a little trash in it and it leaned out. End result was the rings butted and it broke the tops of a couple pistons. And he was not racing... just a little showing off on the streets.
I've never used KB pistons, but I was considering them for my motor. Have you read all their tech articles? The really caution about too small of a gap. In fact they almost promote bigger is better as far as gap goes.