Hey guys....newbie to a C6 here. I have an '07 LS2 that has a significant vibration from 3300-3700 RPM and then it clears up above 4K. It does it regardless of speed or motion. I can rev in Park and get it or I can punch it and the kick down does it, or straight acceleration. Sounds like what 30 yrs ago would have been a harmonic balancer vibration. Vibrates the exhaust too so it's hard to pin down. Could be in my head, but I think I smell a burnt rubber smell when it does it. Any ideas? 
3500 RPM vibration
3500 RPM vibration