[The Radium King]

capristo is a little different than the others. it is designed to bypass most of the muffler at higher rpm ranges. similar to the resonance flap on your intake opening so that more air can move when the cams roll over, the capristo maintains back pressure via the muffler at lower rpm then opens it up as revs increase. hence the big $. this is the same as the 'porsche sport exhaust' (pse) which you can often find used for less than capristo. maxspeed also make a system, but it is either open or closed and doesn't respond to rpm. all systems rely on vacuum valves and elec signals, etc., and, apparently, are prone to failure.

ps, oddly enough, porsche does not claim a hp gain with their pse (just better sound) so there is some sort of disconnect between internet theory and reality. hard to believe.