Glasspacks are old technology, and do not offer near the performance potential of a modern chambered muffler. My experience with them is that they burn out too quick, and become a cop magnet.... They may sound "kewl" when you put them on, but after a full days driving they are nothing more then annoying.... Fast doesn't have to mean loud and obnoxious sounding anymore. I'd just as soon see all the ricers with the fart cans put up with the cop hassles for loud exhuast.... Give me a set of Flowmasters anyday. They cost more, but you usually get what you pay for....