UE 4.24 cooking for Oculus Rift, horrid performance, ok in VR preview

I have cooking/VR/Rift issue Game plays ok in VR-preview inside the editor. The target 90FPS dips to 45 erratically and I started chasing that down.

I tried cooking the game and cooked version (and launching from win explorer) has major issues. I get solid 90FPS on the mirrored capture on monitor until the moment I put the HMD on my head (so it switches on and activates VR). Then framerate collapses to 8 FPS.

Profiler gives me this.