I have them on my 'Cuda. First behind the 500" wedge and now behind the 540" Hemi. Typical glass packed muffler; they get louder over time (years) and the drone is noticeable. But the drone is easily addressed by putting any cheap glass pack (bullet) behind the axle.

Personally, I like the sound; not too loud, I can listen to the radio at cruise. But enough rumble to get noticed. Much like the original exhaust sound, just louder and with some more rumble. Some brands of mufflers change the sound. Everything sounds like a rustang or pick up truck with certain brands of mufflers. The Super Turbos don't do that.