I have the gt 760 and you can add more AI but turn down opponent detail to low,turn down special effects,circuit detail, you want to use environmental reflection on most tracks, don't use SYNC or try it with video card what ever works, use 1920-1080, AA at 16 is ok,maybe add more memory to your computer,use verticalsync with tripple buffering on.
Clean up your computer make sure it is running at optimal performance with less background services running it can't hurt.