Dunno if corvairs had a turbo option or not, but that is where the turbo muffler originates. It was just a lower backpressure muffler, with a throatier sound. I ran one on my '82 GT. The Flow's will probably unlock more power, while the turbos will be quieter. A quiet car can still sound good though.
So, a turbo is a type of muffler. Several brands offer one.
'88 GT convertible, 5 speed, 3:08 gears, A9L Mass Air conversion. Mac shorty headers and H-pipe, Magnaflow catback.