I have to disagree (talking strictly FI applications here). I don't think the gains are necessarily what Kinetix advertises, but I think they are on par with what other plenum upgrades provide, maybe even slightly better. Check my dyno numbers. I have not seen anyone with similar mods (different plenum) hitting anywhere close to my numbers with a Vortech and stock bottom end.
I've always said if you are only concerned with the performance aspect, go with the Crawford plenum. It'll give you similiar power gains for a lot less cash... a great proven product. If you want the power gains AND want something really nice for shows, invest in the SSV.