That's ridiculous, cams don't give you the same power on each car, nor does any mod.
We are only talking about this car. Not claiming that it will give you this increase on every car.
Tell you what, come to surrey rolling road on saturday and run the car, then we'll swap on a decent standard air filter and run it again, back to back on the same car on the same day.
I'll wager you 200 quid it doesnt lose as much as 15 lbft going onto the standard filter, and loser pays for both sets of rolling road time.
That way you can not just prove me wrong, you can also profit from doing so