Many times the mount flanges become pitted or warped so bad that a gasket can’t do it’s job properly and you now have an air leak. This is particularly an issue with thin mount flanges that warp easily due to overtorquing of the mount hardware. I can straighten them to a degree then reface them perpendicular to the carburetor throat or bore. Be aware of proper torque on installation and allow the gasket to do it’s job. If you can’t get a seal with proper torque, it’s time for a new gasket.
Reface one end: $10.00 plus shipping