Nitrous can be very decieving sometimes. Alot of people say that their cars feels stronger when they spray it on the street than they do the track. I know that my nitrous hits extremely hard..but sometimes when i'm going down the track i think that it's gonna go like a low, low 4 (1/8th mile) and ends up going like mid 4's. It all depends on weather conditions too. Alot of heat and humidity like you were experiencing can hurt a nitrous motor. But overall it sounds like your on your way to the 12's. Keep trying..you'll get there
Eric