ITR HP w/mods vs. w/out mods

[itr0878]

I am recently intrested in buying a type r motor lsd for my civic hatch back phantom grey. I use to have a b20b b18c5 ran a 13.3 all motor slicks stock no mods it was sick. I now need help understand c5's hp. I know that if i drop it in my hatch with be quick as hell sick as hell blah blah blah although i heard that with a header intake untuned you will loose hp becuase of how tuned they are from the factory is this true anyone?