Kurgan777

If you're looking to smooth out your framerate, you can rename the folder that contains the leaves, birds, and trash so they won't be shown blowing around, as well as finding the Weather file and turning ALL of the Wind speed options to zero. If your PC doesn't have to recalculate the windspeed every time you enter a new region, it can dedicate power to something else and run that much smoother.
 
You can also try turning down model detail, texture detail, and shadow resolution, and HDR lighting.
 
Basically if you're running low end hardware, making the game look like crap will make it run much smoother.