While I was playing around with the shift+a sound editor, I noticed that all of the cars that have side exhausts actually output their engine noise from the back, rather than the side. It's very easy to reproduce by switching to external/tv camera and doing a simple donut with either LX4, LX6, FXR or XRR and listen the volume change as the car spins around, always being loudest when the back of the car is facing the camera.