This is my rig specs:

i5 2400 @ 3.1 GHz
GTX 660 ti OC Core +100MHz Memory +500MHz
4GB DDR3 1333 RAM
Playing at 1920 x 1080

This is my graphics settings:
Game Effect: Very High
Object: Very High
Particles: Very High
Post Processing: Medium
Shading: High
Shadows: High
Water: Very High
Anisotropic: 16x
Motion Blur: Disabled
Lens Flare: On
Texture Resolution: Very High
Anti Aliasing: SMAA x1

Is there any graphical difference between high and very high texture resolution and how big is the hit towards in game fps? Currently, with those settings I'm getting unstable FPS having lowest at 23 and highest 60 of course. Had random FPS drops on certain areas (Wonder if it's the game problem) Anyone with the same graphics card or similar set up to mine can share your graphics settings with me? Any help is appreciated