Time for a Solo Performance Stainless Steel muffler.
Well the flex pipe held on for 4 months then fully separated one morning on the way to work and I was Loud and low powered for 2 days.The flex pipe breaking at the bottom is super common. A muffler shop should be able to fix that for like ~$50.
I really would put two small exhaust fans there that kick on when the radiator fan kicks on but New York City parkers' would smash themThe rear bumper cover already vents engine heat through gaping holes at the top of the bumper cover.
You'll see them if you look in the gap between tailgate and bumper. The steel crashmember resides in the area you wish to vent engine heat from.
Now you can make those holes up at top bigger, and IMO would give it more of that Porsche 911 look you're going for in doing so.