Well, to be fair, he said "gasses"... which I read as being the exhaust that ends up all over every car.

Even a lean running engine will blow fuel through the exhaust. Pass your finger over the stinger and let some of the moisture accumulate, then blow on your finger a little. That cold feeling is the left over nitro methanol evaporating. These engines do not (and cannot) completely burn the fuel, as there is no true ignition inside the engine like there would be a gasoline powered engine. The fuel mix compresses, then a chemical reaction occurs between the compressed fuel and the platinum on the plug, causing a rapid expansion. Because there is no "explosion" taking place, the fuel does not completely burn. If you have ever flown rc planes, you would know about what the methanol in the exhaust does to crappy coverings.