their claims can't be untrue as otherwise it would be false marketing, but you can set a dyno to read what ever you like.
also i think that the quoted BHP gains are for the one item on a stock car, i think when you start to add more items their BHP overlaps each other.
so if you had 2 items each adding 5 bhp, you might actually only gain a total of 7 bhp.
at the end of the day, they will make a difference, but not a smuch as the manufacturers claim
+1 and I'm after ordering a SSV Kinetix plenum... there is NO way that it will give 30+bhp but it will give me torque and some + hp