Wow! I didn't realize I'd irk so many people questioning an aspect of one rule. Am I influenced by Hot Rod magazine and the stuff they do? Hardly! Did I ever say it WASN'T a "power adder" as Stainless commented? Of course not, it's a GREAT power adder! I was only questioning why it was classified as a "fuel" being it's only nitrogen/oxygen with NOTHING that actually burns. According to Milwaukee it "alters the chemistry" of the gas. It alters it no more than a blown deal. Normal air is roughly a 4:1 nitrogen/ogygen mix which is simple enough. Nitrous oxide is 2:1 nitrogen/oxygen, that's all. Nitrogen is inert and does nothing so all you're adding is 30% more oxygen than outside air. A normally aspirated engine sucks in 20% oxygen, so if we add one atmosphere of boost (double the roughly 14.6psi ambient pressure that we'll round out to 15lbs of boost) we just doubled the oxygen content (40%) of the engine, correct? Now we add double the original amount of fuel and we're back to our optimal 12:6-13:1AF ratio and have more HP. Did that alter the chemistry of the gas? Of course not. With Nitrous, ALL that's being added is more oxygen, that's it and being that it's very cold it makes the incoming air and fuel charge much more dense and "tricking" the engine into thinking it's under pressure. You add nitrous and then you add more fuel (to compensate for the extra 30% oxygen) again to a 12:6-13:1AF ratio and it's just like the blown motors. I wasn't intending to start a fight on here, but it is a forum so I was just asking a question about why it's considered a "fuel" and not a boost issue...