So I recently picked up a VR head, specifically the Oculus Rift, but I've been having massive performance issues with it. Prior to using the rift I played on a 144hz, G-Sync 1440p Monitor with most games maxing out at 144fps at high-ultra settings, but since moving to VR, the same setup, specifically on Project Cars, averages 20-45 FPS on the lowest settings.

The resolution is set to 1920x1080.
Super Sampling, between 1 and 1.5 makes no noticeable difference in FPS, maybe 5 or so.
Texture quality is High.
Texture filtering is x16.
Car and Track quality is High.
Everything else is set to absolute minimum.

A friend, using the same GPU as me, is able to get much, much higher FPS, closer to 80-90, with higher settings. All my drivers are up to date, I've checked Nvidia control panel settings, running cortex, defraging PC, reinstalling windows, verifying cache, changing graphics/resolutions, etc.

I don't know what's causing it. With or without ASW, my frames seem to cap at 45, but most of the time sit in the 30s. Any ideas? Really frustrating playing with such a laggy experience.