It's the tune that gives you the real horsepower.
Companies do a base dyno with no mods at all, then put the intake on. Since a tune is required for the intake, they do the tune as well, then say that the intake gave 35-40 horsepower. If they were being truthful, they'd tune before and after. But none of them do that. Steeda is among the top performers, along with JLT II and C&L Racer.