It's not the nitrous that's the problem. It's the idiots that put it on and don't know how to use it or install it. Mod intakes are known for pooling nitrous and fuel. If you are gonna put spray on a mod motor it should be done with a direct port setup.
I sprayed 300lbs of nitrous through the Booger last year and never had a backfire. If you use it you have to double and triple check things all the time.
Just my $.02