As far as finding the correct jet size:
What you have to realize is that the only constant in this equation is, the Nitrous jet size. size 30=50hp, 32=55hp, 36=65hp, 40=75hp, that doesn't change. A wet system let's you inject fuel in there as well so the manuafacturer gives you RECOMMENDED fuel jets for example if you want to run a 50hp shot, it recommends size 30nitrous and size 17 fuel jet, so let's say you follow this and go to the dyno like i have with the altima, you'll come back with a dyno sheet looking like this:
As you can see you'll be running off the charts rich, so you have two straightforward solutions, A and B, to get that fuel ratio closer to 11.7.
Solution A is you can get an air to fuel controller, and take off fuel that way.
Solution B you can get a smaller fuel jet size and that'll work also, so once you do one or the other you'll bring your a/f ratio closer to a targeted 11.7.
Either way you'll need to 'see' your a/f ratios and for this you need a wideband, to have access to a wideband you also have two simple choices: A and B
Choice A you can buy one, (around300bucks)
Choice B, when you go to a dyno you have free access to it anyway.
and that's pretty much it for findind the correct jet sizes.
But if your confused about anything the simple answer is look at the manufacturers website, check out their recommended nitrous and fuel jets, and follow that except that lower the fuel jet, for example if it says that for a 50hp shot you should use a 30 size nitrous jet, and 20size fuel jet, then just get a 16 size fuel jet and you'll be fine.