Almost everything will affect how the exhaust sounds, even with the same muffler.
Pipe size, number or bends, compression, cam, displacement.
Different engines have different sounds.
A small block ford Windsor sounds different than a Cleveland, with the same mufflers.
This is a fact.^
While mufflers brands AND models within a brand have a the most influence on sound. Other factors will change sound too. Two 5L Mustangs both with Flowmasters but 1 with long tube headers and 1 with short sound very different. Another example is a .484" MP cammed 383 Dart with TTI 1 3/4 headers. Open headers not very loud. Swapped to 509 cam, raised compression and bigger heads. With 3" exhaust into 40 series Flowmasters dumped before the axle. It was THE LOUDEST car Ive ever heard through muffs.
