Yaw makes my FPS low


Depending on the direction I’m facing my frame rate goes from 60fps to about 10fps, as illustrated in the gif.
This is in windows build 686.
It drops looking into my mesh building but rises looking out from it.
I’m also getting high cpu usage 70-80% on an i7


In fact if i set my yaw to anywhere between 0 and 60 degrees my fps drops to 10 above that it goes up to 60 fps
But only in the sandbox.So I’m thinking maybe a mesh model with a none standard poly in it- ngons and the like?