@fox134 Well lets hope you don’t have an ipxe.exe in there…
The client gets its booting information from (the) dhcp responsible for assigning an ip address to the target computer. So if you want the target computer to use a different boot file then you might update dhcp options 67.
Now with that said, from your OP you say that FOG is giving out the IP addresses on a dedicated imaging network. So if you want to change the boot file, you will need to edit the dhcp config file on your FOG server.
You will see for arch 7 and 9 it calls out ipxe.efi. You can replace that with maybe snponly.efi or any of the other efi files. Then you must restart your dns server. On ubuntu you would issue the command sudo systemctl restart isc-dhcp-server to restart the service.