JMO, get an AFR meter.
You're giving up a bunch with a vacuum carb as well. That's another soapbox.
Pig Rich on a nitrous engine is WORSE than lean. It will run and beat itself to death. Lean it will barf on itself. A little rich is OK. Pig rich which most of the old jetting suggestions from the manufacturers printed were horrible. Basic deal in general, if the fuel jet is larger than the n2o jet, it's a pig rich tune up.
Find the best MPH for you car on carb only. Note the AFR. Tune the juice to the same AFR. Pretty simple approach.
How you decide to plumb it is up to you. Know plenty of guys running 150 shots with a mechanical pump. Separate regulators for carb and juice. You can tune the juice a little by increasing/reducing fuel pressure if you don't have a larger selection of jets. Want leaner, turn pressure down ever so slightly. Don't make 1/2 pound changes, make them small.
Juice is addicting... signed a N2O junky from the 1980's when we were just learning. Ask me how I know about pig rich... Burning plug electrodes, just feed more fuel pressure... wrong...
plenty of stuff that when torn apart looked like garbage, but still ran! I still love the stuff!
