@EA_AticHe did in #5
Oh, just looked through it myself, I see that the monitor is 60hz - so see if there is any vsync on as this will limit your FPS to 60 automatically because your Monitor cant display any more FPS anyway.
But still that 90 to 100% CPU Usage makes me worry. If CPU is somehow overworked / working bad / buggy whatever and at 100% Usage it has no time to tell the GPU to render a new frame, thats because low FPS and only 20% GPU Usage...
But first check Game Settings: Video - Advanced - Future Frame Rendering ON and Vertical Sync OFF and see if that helps.