I noticed a few sound issues:

Legit bugs

• The engine sound panning appears to depend on the kart's heading relative to the world, not relative to the camera, so sometimes, you can barely hear the engine, and sometimes, the sound is coming from the left or from the right even though the kart is straight in front of the camera. It's like the camera's "microphone" has a compass and is always facing north (or maybe it's the engine sound that's stuck facing north?). Try driving in a circle in an open area and you'll see what I mean!

Not sure if bugs

• The engine sound pitch/speed seems way too low? It sounds more like a bus than a kart...
• While driving at full speed, and without letting go of the accelerator, the engine sound pitch/speed will briefly drop, as if gearing up, only faster.
• Most of the time while driving, there are no ambient sounds. Sometimes, when the water is in view, you will hear a splash or two. I guess none of this matters in multiplayer, though :)

Also, not gonna lie: Seeing the graphics, I was expecting Koopa Beach-style music, and I was a little disappointed there wasn't any :) Not an "issue", though!