Mmm none that I know of. I think there are a few mods that enhance the graphics settings though, I know Ryosuke made one but I think that one is intended more for increasing the game's quality, not performance.
Try it though, who knows. Anyway if you don't find a solution you might just have to disable anti-aliasing or lower the resolution...
EDIT: Also try your graphics card driver settings, Nvidia give you the ability to disable or enable certain features for every game. I don't know about ATi though.