I just cant seem to figure out if there is something I can do to fix this, or if the game is just... not-so well optimized..?

I have a GTX 590, i7-2600, latest nvidia drivers (SLI is functioning)

In the first bit of single player, I'm finding the graphics very instable and inconsistent. If playing on 'High' preset In sheltered areas and rooms I can get 50-60 FPS, but as soon as I look into the distance my FPS will drop by half. Even if I tweak graphics lower to Medium, the same general rule applies, just with slightly higher FPS. I've never encountered this level of instability in another game and its incredibly disruptive.

Also I have very selective input lag. All movement is fine, but switching guns (keyboard), looking down sights, and (sometimes) firing, has about a half second delay?

With my system I figure I should be breezing through this at medium/high presets. Never had any issues with the older Crysis'. I tried the power management change in the nvidia control panel already...

Is anyone else encountering this?