Stand next to Devrim Kay in EDZ church and make sure you are running at some sort of framerate cap which is smooth (verify by slowly rotating view). Now let the game sit in the background for about 20-30 minutes. Then come back and rotate your view with mouse/joypad. You'll see small fluctuations in FPS from your set fps CAP. For example mine jumps around from 60-58. Now to really prove it has nothing to do with headroom of your PC just remove vsync or up the framerate cap and you'll see it starts stuttering at your new cap with 1 or 2 framerate variation. None of the video settings change this behaviour.