Have you messed with RenderAheadLimit at all? The default is 2 limiting the CPU from rendering only 2 frames ahead of the GPU. Some say setting to 0 ( disabling it ) will give an FPS improvement. Others say they get this increase but with input lag.
Mine is set to 2 but I was gonna try 0 and see what happens. The original BETA had 0 as the default and I remember getting input lag back then but I was also on a different rig at that time.