Now...how about you go and pull the numbers for the actual car he's looking at an intake for. Civic HX/EX.
7.3 and 18 are not significant gains.
And that's not a couple of examples. That's one example of 30+ HP. But the 30+ HP is on a motor that is very modified from its stock version and continues to use the stock intake.
Now go find me a chart for a Civic EX/HX that shows your 30+ HP gain from an intake.