with a turbo set up you will have your boost set and the waste gate will open, at what ever set point you decide on so regardless of rpm you won,t exceed that boost setting, now I am not that familiar with the superchargers,but I would think it may be possible to gain boost with rpm as you have a set of pulleys which is direct drive based off rpm. so if you exceed that rpm you could gain some boost. but I would be sure there is enough safety margine in your set up as to not exceed the designed cfm or speed of your supercharger, I am sure somebody with more knowledge of the supercharger set up will correct me if I am wrong. you can do as MIKE did and set up the nitrous to come on until you reach a set boost level and then it shuts off, that would eliminate the over reving problem. I had mine set up on a push button and just held it open from the time I hit the throttle until the race was over. if I was racing other wise I used it as I needed.