Question about how to play through certain areas without FPS drops.

A majority of the time I play the game, my fps is at a consistent 60. But when I get to certain rooms in some levels, my fps suffers quite a bit, almost getting down to 40 or below. So my question is how can I stop the fps drops? I already use CPUcores, but it doesnt seems to help much. Would I have to buy a new Graphics Card or Processor? I don't like having these drops.