Gpu passthrough issues

My issue is that I am unable to get gpu passthrough working because when I get to the step to modify grub it gives me this error when I do sudo update-grub "/usr/sbin/grub-mkconfig: 40: /etc/default/grub: vfio-pci.ids=1002:66af,1002:ab20: not found" I also tried switching it to my gpu's value and its the same error just with my gpu address instead of the one that is provided in the directions.
