[jmatta]

I installed the Evo years ago and notice a discernible difference in sound from stock; the sound is just plain louder and howling at full throttle. I've driven numerous other stock intake Boxsters and the intake sound isn't even close to the sound my car makes. Whether there is a gain in HP, it would be negligible; but the sound is tremendous.

Don't understand why you have a different experience, as I can't imagine the displacement difference would account for the distinct sound.