I actually think it doesn't sound as bad as everyone said it does. I think it sounds less "tinny" now. The original Ferrari sound was annoying to me, but now I can actually hear the turbo and other aspects of the engine.
Maybe I'm crazy.
But, just because you don't like something doesn't make it a bug. The engine sound is DIFFERENT. Not bugged. And not liking a sound in a game doesn't make a game unplayable.
Something that might actually be a bug though - the Ferrari engines are super quiet for me compared to all other game and engine sounds.