CTRL + `

(The tilde key [this key: `] can be found next to the 1 key, above the tab key, and below the ESC key.)

Similar to Bioshock, this game uses locked animation refresh rates.

This means that though your FPS may be 144+, the game will still retain a "ghostish" image that is not usually distinguishable on 60hz monitors. The console command lessens the effect of this ghosting (I don't know why) and gives a minor framerate increase.

If you know how to resolve this issue fully, I can update the guide and credit you if the fix works.