Hmm, that's interesting, my '13 was so quite I had a new pair of mufflers ordered within a week of me buying it brand new like you, haha. I wonder if there is a difference? I could barely hear the mufflers at all over the engine noise.
In normal day-to-day driving I can hear my stock muffs out the back. It only makes sense that there will be resonance (drone) at some point in that case. It's an audio frequency thing. So the question boils down to why I can hear my mufflers while almost everyone else can't? I've posed the question in the allfordmustangs.com forum and had only one respondent out of many that claimed the same thing I do. There is resonance (or drone) as the engine passes through 1900-2000 rpm especially under load. Everyone else claims to have quiet stocks and basically look at me as a loony..
Could it be that all these respondents have had loud exhaust in previous cars that blew out their hearing?
No mods. The car just turned 1000 miles 2 days ago. Its sound has changed over the 3 weeks I have had it. I suspect the car is somewhat broken in now and will now settle on its own unique note.