Based on what I said above, there is definetly a "new" style exhaust set-up(i.e. how it attaches the pipes. The only problems is proving it to your dealer. Without a TSB, the dealer only has what you say as a basis to go by. Try taking your car into the service department and asking them to contact STAR center about your vibration. Actually, I just performed a STAR online search, there are updated pipes and spring nuts available.
a new flex joint has been released to break up the mode. In order to fix the car you will need 2 pipes and 2 spring/nut assemblies (Mopar call out either a nut or spring, depending on the system. It's the same) The part numbers are 04581868AH (qty - 1), 04581869AG (qty - 1), and 04578363AA (Qty - 2).
They claim the vibration is present between 1500 and 2000 RPM.
Unfourtunately, there are only 12 muffler assemblies available at this time in the US, only 9 resonator assemblies available, and no spring/nut assemblies.