I've been having sound complaints on my driving worlds and this is the main problem. The car sounds cannot be lowered on the audio volume because it's using another type of unity standard audio source specifically for cars, best thing I could do for now is just lowering the volume of the audio file itself but sometimes that's a bit too much work. It would be good if it can be implemented into the World Volume, I guess the devs overlooked this because they never expected people to be making driving worlds for VRChat.