Have either of you ran nitrous on 3.73, 3.91,or 4.11 geared cars? From what I've researched, higher gears (in this case 3.55) do better with nitrous, than really low gears.
Second, you don't make a bunch of power and you ain't hitting it with a big shot of nitrous. So gear and converter should be chosen accordingly.
Also, you didn't chose a cam that is ground for nitrous. You'll make more power on the nitrous (and less power N/A) and have a much wider tune up window if you buy a cam for nitrous.
