try grand turismo 4 for ps2. that actually could be grand turismo 3. Great Game... Very very fulfilling has damn near every race ever(if not then a plethora of fabricated races). I think the game is classic. Try it out.
Also if this is for a xbox emulator(which i never touched simply because the xbox was... mehh) anyways play around with all the settings. You could have an interpreter as what ever runs the game and those are slow. Good for something like gameboy emulation or something because it's more on the fly but for something as resource expensive as xbox definitely go with the compiler options.
Other things... Graphics libraries you're using. If windows, try directx. It could be set to something else.