Lenz,
just about nothing drones worse than a flowturdmaster. I can't comment on the Borla, but I've had flowturdmasters, the flowturdmaster deltaturd, and all the other mufflers I will comment on.
Any glass pack will sound good, but LOUD.
THe spintecks I had just sounded crappy all the time.
THe Dynomax ultraflow SS is the choice for power, quiet idle, lots of bark at WOT, some drone at highway cruise, but not nearly as bad as a flowturdmaster.
Next is the Dynomax Super Turbo. (or probably any similarly built turbo muffler) More restrictive than the Ultraflow, but nice muffled sound at idle, but still lets you know it's a hot rod, reasonably quiet at WOT, and just a little drone on the highway.
Then you have a Hemi muffler. Very similar to a turbo muff, except no drone, and less restrictive.
Last is the quiet-flow. Very restrictive, but OEM cadillac quiet. When I was daily driving my 500 inch Elcamino, I wanted to hear the radio, have conversations, make business call on the cell. THis was the only muffler of the several I tried that was really quiet behind that hotrod mill.
Here is my Ultraflow SS's at WOT from outside the car:
https://youtu.be/snKfkP8nqg4Here is some cruising around with Ultraflow SS's: (no carpet padding or sound deadener, 735 horse hemi, 2.5" from the manifolds to the rear bumper)
https://youtu.be/nKfPiVjUdjU?t=2m51sI like them.