Well we need more information to see what’s really going on, press ctrl+shift+, for GPU profiler while you’re in stereo mode. The first profile you do takes UE4 longer and usually messes up the timing, so wait a second and take another profile then post that. Also to make it easier to diagnose, post your system specs, the rendering quality settings you’re using, and a screenshot of what you’re looking at when it’s at 22.2ms.
The 22.2ms comes because it’s double 11.1ms. The rift and vive both want to render at 90 fps (i.e 11.1ms per frame) so that people don’t get sick. They also need to have the whole frame rendered before showing it so that it’s not showing half of the previous frame (screen tearing) and they fix that with V-Sync. This means that your game has to render each frame in 11.1ms or less, but if it takes 14.5ms to render, it misses it’s time window to be displayed, so now it has to wait for the next frame so it can display. This is why people sometimes see 22.2ms, because the gpu can’t render fast enough so it can only display every other frame. Don’t underestimate how much more rendering power VR takes, anything that has to be done for every pixel, like shadow filtering and screen space effects take way longer to render in VR than normal games, for example a scene might render in 4ms in a desktop window, but take 15ms in VR.