No doubt v-sync enabled.
I have the same monitor and a 4k monitor..
https://m.newegg.com/products/n82e1...B6YqvEI_rsXis1LE2aMaAlaeEALw_wcB&gclsrc=aw.ds
Turn off v-sync in the game options and make sure g-sync us enabled in the nvidia control panel.
Also in the monitor settings you may want to try the overclocking settings to run it at 165hz.