I might be able to throw a bit of light on the NO2 use possibly. I'm also a drag racer like Jerry, and have used it for 20 years on different stuff.
NO2 is a really cheap way to get HP our of an engine. That's it. It's cheap. Becasue of this most people get greedy and want more, don't tune it in properly (fuel/NO2 mix ratio MUST be right) and a loud bang follows. Get the mixture right and most engines can take an enormous amount of power, get it slightly off (when your close to the limit) and get a new motor.
I put 50HP into a Kwaka 1600 cruiser, because it was the CHEAP way to get enough HP to qualify (I need to run at least 11's) to run at my National drag meets.
I put 40HP into my S4R Ducati, coz it was the CHEAP way to get the thing to run in the mid-9s at the track and put the wind up the Busa's!
I threw 150HP at my Supra years ago.......shit I can't remember why, but I'm sure I had a good reason at the time!
Anyway, I also have found out over the years that when the HP level gets too small, the orifice that meters the NO2 can, as a combination of extremely small size (less than 0.010") and extremely low temps (NO2 will instantly frostbite anything on contact, VERY cold) actually freeze shut. The size seems about the 0.008" or less mark. This is at around the 8HP level roughly. Since with most engines, stock or modded, a safe NO2 HP level is around 30-40% extra, this means that it is very difficult to tune or get reliable NO2 use out of engines with less than 20HP.
I rekn gearing is a MUCH better way of multiplying torque at the tyre.