I recently updated my PCs motherboard and CPU. After doing this VR Preview are running at 5-6 fps 
Anyone experienced this?
Display adapter: NVIDIA GeForce GTX 980 Ti
CPU: Intel i7-6700K 4.00GHz
RAM: 32 GB
Windows 10 64bit
Have you checked that your cpu heatsink is on properly? I had this problem when I last upgraded my cpu, The heatsink wasn’t on properly and would limit itself so it didn’t overheat.
Long shot but may be worth checking your temperature just incase
What motherboard? Do you have any conflicting software, such as Sonic Suite, running?