Adding extra fuel in puts more strain on the coil and ignition system as it takes more energy to get the spark to jump the plug gap.
Play it save and start with a plug gap of approx 0.025 and see if that helps.
What ignition system are you presently running and where do you have the plugs gapped?
Here is what I think, and at this point it is only a guess. Need some more data to either confirm or unconfirm my idea/guess. But I see it a lot, not usually as pronounced as with your car. Unless you have like twin foggers or something like that. But I think when you engage your solenoids for the NOS it is cause the voltage to drop, which is causing the coil to break up. You could have a bad NOS solenoid, or just need a bigger alternator. Typically it is a bigger alternator. Hooking up your data logger will give you the information you need to determine if this is the answer to the problem.