1986 Chevrolet Caprice Not the normal 305 engine sound!

Chevrolet Caprice 1986 Classic Brougham
305ci 5.0L (Stock) -Single pipe exhaust
Low engine note:
My friend have the same caprice that I own except that he have the dual exhaust version, yet his engine and exhaust sound a lot louder than mine and more like how it really should sound. The engine runs perfectly fine and respond to the pedal, but it really sound low compared to other 305 5.0L engine.
Burnout problem:
The other thing, that when I try to do burnouts (push the brakes enough to stop the car, and floor the gas pedal), The engine wont rev high like it should be and stays about 3000rpm and the tiers spin a little bit and loses power until the wheels stop and the engine keeps the 3000rpm. But the engine revs high when flooring it on high way.