I agree with zope pope, you need a hole in your firewall for air passage. The carb air intake is flush with the firewall and that just won't work. You're going to have to remove the engine to cut the hole so you can look into the carb intake at that time to see the throttle butterfly. You can get familiar with your carb at that time and make some notes which way your throttle arm should move. How big should the hole be? I'd make it at least 1 1/2" and larger will not hurt anything. You can cut it with a small hole saw. I don't know what airplane you have and whether there is free air available in the box behind the firewall. A large hole will allow free airflow around the carb. If in doubt, make the hole as large as possible without sacrificing firewall strength for the standoff engine mounts.