I’m assuming that this AC system is using the same air ducts as the heating system. If it’s less than 10' between the combustion chamber – return, and / or there’s not enough combustion air in this room you’d need to hire an HVAC professional. It’s difficult for me to give you some kind of a solution because I can’t see this area, furnace installation, and I don’t have its technical data. You’d have to provide a few pictures and a lot of details that would be critical in answering it.
Start from reading those two articles, maybe they will provide enough help. Let me know.