N/A = breathing on its own with no power adder.
Forced induction would be a super charger or turbo.
Nitrous is a power adder but not forced induction.
If you look at your first sentence, then your last one, you are in fact saying that running nitrous means your are NOT NA. Probably just a typo, but why would you consider a motor on N20 NA? You are in fact forcing a gas into the combustion chamber that allows more fuel to be added and burned.