When I started researching/test driving R/T's in early 2010 I was lucky enough to come across an extremely knowledgeable salesman. I noticed the 6 speed models had a deeper exhaust tone and were louder than the automatic cars. what he told me was the stick and auto models have different exhaust systems due to the MDS. The auto models had to have the exhaust corked up a little tighter to prevent the drone when the car goes into the 4 cylinder mode. 6 speeds have a different system that flows a little better and is slightly louder. You should be able to resolve the problem once a tuner is available.