do you actually gain anything from putting one of these on if your naturally aspirated? if so what could you expect?

 

I assume you mean an adjustable one. every honda (92-00) made in the US has a fuel pressure regulator.

the only thing you can do with it is adjust your fuel pressure. Which if your car is tuned properly should never be touched anyway.
If you're running on the stock ECU a touch more pressure may give you -5 to +5 hp but it will drop your mpg for sure.

I have one and almost regret getting it.