Performed heater tune-up on a Carrier gas furnace system. Checked the electrical, mechanical and performance systems of the unit. Cleared, cleaned, flushed and treated the drain line and cleaned the exterior of the furnace. I did find the flue pipe was leaking carbon monoxide at the inducer and flue pipe connection. Repair options were presented to the homeowner and he chose to have the flue draft hood connector replaced. I replaced the connector and verified there is no more carbon monoxide spillage from the furnace system. Flue pipe is clean and clear of obstructions. System is now operational.