I'm running on I5-3570k (3.4 mhz ) 12 gb ram, 1080 card. Everything on SSD. 
Oculus Rift CV1. 
On some maps i get FPS in 120+ range most of the time. 
In some cases, it drops to 20fps, last night for example. 
It appears to be map related. Do you guys have similar experience ?