Steam overlay ruins hitreg and fps.

[FURRYDISEMBOWELER74]

I had complained quite a bit before about the hitreg and I never got to fix the issue, but recently I tried dissabling it(steam overlay, sorry for not specifying when I created the topic) and all the FPS issues in casual were gone, fps went from 150-160 (and the drops) to over 300 constant without even a slight dip and almost all the hitreg issues were just gone, they just dissapeared, my accuracy went up, my headshot % went up, my kd started going up and I ranked up easly as well. What I don't understand is, why does steamoverlay cause this ♥♥♥♥ for me?