One of the combustion products of nitromethane is nitric acid. The main reason for a gas mask. Adding it to the fuel isn't going to add power. Any alkalines in the fuel increase the risk of explosion, to nitric acid will make the fuel safer over the long run.
He could have been running picric acid, propylene oxide or hydrazine. All were in use at one time or another.
If the ground is shakin; and the flames are green, he must be using that Hydrazine