I had Borlas in their side exit system. It might have sounded different because of the restrictions. It was just pretty quiet unless I was @ WOT. Then it sounded pretty good!! I don't know anything about anything, though! I am dumber than a rock!!
The Borla Stingers with an O/R H pipe will be insanely loud but nice! LOl...I love the sound of the Stingers...just couldn't afford them, I have the Magnapacks...sound great too. Flowmasters have a great sound too depending on model ...give us the exact ones you are thinking of...
I have a cousin who used to have Mustangs. He loves Borlas. When I got mine, he said they were the best! They were just high $, to buy! He still likes them over any other brand.