I have adjusted the mouse settings to use raw mouse input, this has resulted in having to re-scale the sensitivity settings so you may need to adjust your player and vehicle sensitivity settings.
I'm hoping this fixes issues people have been having with the mouse input, if not let me know which issues you are having and whether it is with the vehicle camera, first person camera, or both.
I have also added an FPS limiter, if you have high-end hardware and your GPU has been running hot, try setting the FPS limit and see if that lets your GPU run cooler.