I've read most (many? All?) new c5's have a lumpy idle and are prone to stalling, but I'd like to know.... when does it go away?
Maybe it's an air leak around the rubber boot on the intake side. Or gasket.Or airbox. Have you checked them? Maybe spritz some carb cleaner around the connections? Let the motor cycle, and see if there's a change in the Idle?
I wonder how the short Watsonian "sports" exhaust sounds. I wanted more bass, not necessarily more noise...!