Major FPS drop after tabbing back into the game

[WolfenswanFA 19]

I've noticed that my game perfomance will decrease to the low 10s when I've tabbed out for a bit. Switching the display mode will restore FPS to their normal levels, until I tab out and back in again. Whether I'm on fullscreen, fullscreen windowed or windowed doesn't matter.

Any ideas what could be causing this? I don't remember having the issue prior to roughly 1.54

Edit: Turns out the moment I make the post I figured out a solution: Using -nopause as an additional start parameter and setting CPU priority to "high" seems to have fixed it.