I had been using Nvidia Inspector to force on Ambient Occlusion with the Fallout 3 compatibility profile (at the recommendation of someone in another thread somewhere) and I just realized that was the cause of this flickering shadow issue I was having. Basically i noticed that the flickering was coming from a dark halo around some objects that is apparently an illusion to look like it's casting a shadow on the object behind it (it looks horrible to be honest). I remember the black halo in The Witcher 2 from using ambient occlusion and i put 2 and 2 together. So i switched the compatibility mode to Dragon Age 2 (not sure if it's even working now) in Nvidia Inspector and it's gone and I'm getting another 15 FPS.