On my Onevia i had a custom exhaust, which had 2 magnaflow mufflers fitted from cat back they are a high flowing muffler and i passed epa with that system on, there was absolutely no droning, although it was not a cannon. And still sounded awesome, it was probably one of the best sounding RB engines going around except for the RB26 of course
Ps. They were 3" inlet and 3" outlet but just a normal shaped muffler