Joining this thread a little late, but just wanted to describe my experience with the TRD exhaust that I had on my 2013 BRZ. I definitely had an exhaust leak, and the flanges were somewhat warped, which resulted in drone coming and going as the exhaust system warmed up. I guess my installer over tightened everything.
Half the time there was no drone and the exhaust was perfect. Just enough growl to make things fun and interesting. No drone, even on highway drives. I absolutely loved driving the car then. The other half, the drone was just unbearable, and I would curse myself for getting the exhaust. Could barely hear the radio. But then it would go away, and I would be in love again. I tried fixing the leaks, adding extra seals, re-torquing everything, but eventually I gave up. I sold the car after owning it for just over two years as I went to grad school. I just bought a 2017 BRZ, and after my past TRD exhaust experience I plan on keeping the stock exhaust. (Also a bit older now and prefer a quieter ride
)