Did you try Racer without shadowmapping ?
I got x3 more fps which enables me to play correctly in ultra widescreen mode. (3 monitors)
I tried the no-cg version & I get around 600 fps which is really ridiculous...
All I can say, you buy an 1 year good GPU quite cheap nowadays & bye bye the no-cg version, no more struggle... Ruud is aware of optimizing algorithms which makes Racer so great in cg version & he will stick to it more & more in the future.