TTI Exhaust

I think 2.5 is perfect, and it may fit better. Unless you have a serious race car
It's all in what you like. 2.5 for all my stuff.
An open 2-1/2 pipe or one with a glass pack type of muffler (straight through) will handle 600hp.
Agree. But others may feel different. My 472 Indy Hemi Belvedere ran 2 1/2 with DynoMax Turbo mufflers. Not a problem. BUT it was a street car only.
Yes, I'm sure it gave up horsepower but was quiet until the loud pedal hit the floor.