i went from a mac o/r-h to a bbk catted-h on my old lx. it quieted it down a bit, though it was already pretty quiet because of the 50series flows. i hadnt had the car for more than a couple weeks before i made the switch, so i cant really tell any performance difference, but it didnt feel any different to me. personally, id avoid the bbk unit though, it was a pita to get in there and it seemed to pull the catback towards the front of the car. im going to go with a mac hiflow-h here in the next few weeks, hopefully it installs a little easier.