I have NPP and its plenty loud. My flanking neighbors have each texted me when I arrive home. It's that loud they can clearly hear the car in their houses. Al Oppenheiser even says this was their design intent to make a statement your neighbors can hear.
The Camaro NPP has different programming than the Vette NPP. On the Vette it's quiet at idle and loud at rpm. On the Camaro it's loud at startup then quiets down for a certain rpm range then gets loud again. The exhaust commander switch basically makes it loud or quiet around 3K rpm. When loud the car certainly drones more. I liked this at first but now appreciate Chevy's programming of the valves. I can actually hear my radio better now and talking on the cell phone more comfortably. But if and when I want to get raucous I can push the Exhaust Commander button and go loud again.
Oh, and when you're in the loud mode the backfire / back gargle is much more prevalent and delicious.
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