At 1,300 miles I started noticing almost a rattling noise from my muffler upon startup or tweaking the accelerator. Would also hear it on downshifts..sometimes. Best way to describe it is the sound of metal inside of the muffler somewhere. Anyway, dealer inspected and said they needed to replace resonator due to something came loose inside and was now vibrating. They had to replace pretty much everything from mid car to the exhaust tips. Got it back today and it seems fixed. Sounds great again! Just wish they could have given me credit towards a different cat back or something.

Wanted to share this if anyone else is having the problem