This past week I found out how effective a
resonator can be in taming my BTG Axle-Back single exhaust. The BTG axle-back exhaust system is LOUD--especially around 3000 RPM when you hear the "harmonic roar" that plagues many after-market PT Cruiser exhaust systems.
This noise further increased recently when the Mopar STAGE 1 Turbo Upgrade was installed. So, I finally had a 24-inch resonator installed between the cat and muffler which eliminated the problem. You now can hear the radio with the moon-roof open, but, more importantly, my wife is happy.
You still hear a distinct custom exhaust sound--sort of a "low but very mellow 60's Mopar sound". [8D]
Furthermore, I now can hear my new Mopar STAGE 1 Turbo Machine spool up and move out ever so fast 
like never before. [8)]