I played around with the jets on my NX system as well. Initially with 41/24 jetting I gained 85RWHP/137RWTQ, but the A/F pegged below 10 and was running VERY rich. I tried dropping to 41/22 jets, but there wasn't much of a gain, so I went up to 52/24 amd the A/F was 10.5 at it's highest point with the nitrous engaged and I managed a 112RWHP/147RWTQ gain compared to N/A.
As Tom mentioned it's important to take into account that the added air pressure of running at higher speeds will naturally lean out the mixture when actually driving the car. So it's smarter to dyno rich and take a small hit on the power for the sake of reliability.
Another point is that simply adding more power is not automatically going to make the car faster. in other words more is not always better. After a point, the stock tires are going to spin. My 1/8 mile times/speeds are not dramatically better (with stock tires) with the nitrous, but I'm picking up 8MPH in the 1/4 mile.
The big difference is seat of pants for me on the street. Adding the N2O feels like I dropped down a gear or two and are always in the meat of the power. This is especially nice on the freeway when I'm in 6th at 70 and switch on the N2O and it feels like I'm punching in 4th.
I have a fuel pressure and WOT switch, remote bottle opener, gauge, and bottle warmer.
When you are dynoing, it's important to check the bottle pressure as 100psi difference can cost 50-80HP.
I use a MSD modded window switch to trigger the nitrous. Then you are assured to only trigger the nitrous when you are within an optimal rev range, not at low RPMs or in between shifts. Remember that the Viper does NOT have a knock sensor, and if you hit the rev limiter (easy to do with N2O) it automatically cuts the fuel to slow the engine. And if you have a hand triggered system it can quickly go lean at high revs.
The Window switch is around $85, and $25 more for MSD to mod it to run in 2 cyl mode for Viper 10cyl engines.
I personally wouldn't run nitrous without a window switch.
I was going to use a progressive controller for the nitrous, but the fact that the design works by strobing another solenoid and that you need to have a backup solenoid in the system because it is anticipated that the primary solenoid WILL fail was not a good system design for me.
I had worried that having the nitrous at full power in 1st and second gears (especially with 3.55 diff gears) would spin terribly. Which is why I had initially bought the progressive controller. But I raised the RPM trigger on the window switch to 3200RPM, and short shifted into 2nd at 4500 RPMs and the car launches predictably and quickly for stock tires.
Certainly I can run better 1/4 mile times with slicks or drag radials, but then I'd want to add HD halfshafts, a rollbar, and 5-point belts to not get kicked off of the track. I'm already pushing it.
-Dean.
