A lot of tests later, my friends still have big performance troubles in all situations, with ki, without ki, they went down with graphics and supersampling and still have massiv fps problems... before 1.109 everything worked very well, we drove all with nearly the same settings, this is impossible now, they reinstalled steamvr, no change, reinstall rf2, no change... there must be something wrong with the vr version of 1.109... cant be the hardware, both have i7@4,4ghz, 16gb ram, gtx1080 with driver 385.41, w10 prof , with this hw and middle graphic settings rf2 must run a lot better than 40fps in vr...
And the strangest thing is that i dont have this troubles at all... i5@4.2ghz, 16gb ram, TitanXP with driver 385.41, w10 prof
After this fu** testing with no result, we drove a round with AC, everything full, 2x sgsaa and 1.6 supersamp and had no performance problems at all and a lot of fun !