I was able to reproduce the wall clipping bug on a Linux machine, running at ~20 FPS with a very old integrated nVidia card. The car would keep going up, to the point I was above all of the scenery buildings (and drifting middle-air!), but if I went back to the track route the car would eventually teleport back to the track's surface. On OS X, on the other hand, I wasn't able to reproduce the bug.
Linux (Xubuntu 14.04-amd64) test machine has a Turion 64x2 processor @1.6 GHz, and a nVidia GeForce Go 7150 card (~20 FPS on lowest settings at 800x480). Both the 32 and 64-bit builds exhibit the issue.
OS X (10.10.1) test machine has a 3rd gen dual-core i7 @2.8 GHz, and an Intel HD3000 card (~60 FPS on lowest settings at 1280x800).