Spiking GPU lag in VR


I’ve recently got a HP Reverb G2 and running on a 2080. I got AMS working well with settings around med, at 90hz but using reprojection. In most cases, I had a smooth 45FPS, with usage about 60-80%. Of course, lag is higher with reprojection, but always orange or green.

Without changing anything, I’m now having issues. Sometimes the game runs well, but other times I’m loosing 10-20% FPS and getting purple spikes in the GPU lag at regular intervals, along with a lot of dropped frames. Today I ran a practice session at a track and the game ran fine. I turned my PC off and came back to it a few hours later. Same session, same settings. It was stuttering badly.

I think Steam VR may be eating up GPU resource, but I can’t tell in game. And I can’t start without steam VR being on. Or it could be something else.
I’m really annoyed because this ruins the experience. Yet to see if it is happening with other games, but I guess it will.
Any help appreciated!