I have never been happy with my BTG axle-back exhaust muffler (even after adding a resonator) so it recently was replaced by
Mopar performance duals. BTG claims their single axle-back exhaust is not loud on a turbo but, from my experience, it was very loud on my turbo and had a bad "harmonic drone" at 3K RPM until a resonator was installed. So, after almost two years, I decided the BTG had to go.
The Mopar performance 2.5-inch stainless steel free-flow dual exhaust system by Borla was recently installed on my STAGE 1 Turbo GT and I'm very pleased with it. 
The system is custom-made to fit the 2003-2004 turbos so it is a perfect fit. While I am not sure if I gained any additional horsepower the larger pipe lets the turbo "breathe better" and it seems to "spool up" faster. The sound is awesome. My Cruiser now sounds like a finely-tuned Indy 500 race car instead of a street hot rod like it did with the BTG single axle-back exhaust. [u]There is absolutely NO harmonic drone</u>. The
Mopar stainless-steel dual exhaust is right for me--sharp-looking, great sound, and a fine performance addition to my S1 turbo car! [8D] [8)]
See PICS of my
2004 Seamist Green GT-146 Limited Edition Cruiser at: http://www.ptcruiserclub.org/galleri...2/gallery1.htm