K&N Substack ?

Ok I'll admit it I've been lurking on this site for some time now and have decided to show my face :confused:. Just a quick bio for history sake. I raced A/B hydro's and utilities back in the late 60's early 70's. Had to give it up when I went off to college :mad:. Anyway many years and boats later I have picked up a 16' Donzi, rebuilt the engine swaped drives ect ect. My questions is has anyone had any experience with the K&N substack that fits into the throat of a carb( http://www.knfilters.com/Racing/stubstacks.htm). In theory it is supposed to even out the air flow as it gets sucked into the carb. They claim modest gains in the range of 20-40 cfm which might give you another 8-20 hp depending how the carb is jetted............any thouhgts. By the way if this thread belongs in another fourm just let me know.

THX
Sam