The one thing to keep in mind is that the more nitrous you inject, the more likely you will have errors in the a/f readings. An engine simply can't use all of a big shot of nitrous and a lot of it winds up getting pushed right out the pipes. When you shove raw nitrous across the O2 sensor it isn't reasonable to expect that the readings are still dead-on.
For this reason, I would pay more attention to how much fuel you are using in lb/hr, how the car feels, and looking at the spark plugs than an O2 reading in a nitrous application. I have a feeling that your end result would be similar if you did it this way or did it Cal's way, but because of the possibility of false readings from the O2 sensor AND the fact that nitrous is some scary $#!+, I would recommend to go by fuel consumption and plug readings. Make absolutely sure that your injector flow rate is properly entered in C-Com to ensure the most accurate results.
