Any s3tc game will not work for the same reasons, like Quake4.
It is not so obvious from the Torcs code. There is a loop over strips of primitives (could be triangle strips) and it renders each strip using glDrawElements. The problem is some models have one strip per triangle. They don't seem to optimize their models enough.
Aren't there automatic tools for that? ACTC?
If you start the game, how many fps do you have at the starting position in the track called Forza on r600g?
Torcs caused my Juniper (5750) and X instance to lock up badly. Dmesg nor Xorg.log showed nothing of interest.
git -mesa, -libdrm and -xf86-video-ati