Performed inspection on gas furnace.. Cleaned flame sensor … Started ignition of furnace found indicators of heat exchanger issues on system … found rust present inside heat exchanger also found rust and decay on press ring and found crack in heat exchanger and also rust decay found in burn tubes… Also found pitting in heat exchanger.. Inspected blower wheel and motor are lightly dusted.. Inspected evaporator coil and is clean… Inducer motor running normally at this time. Checked carbon monoxide throughout home and found to be in normal levels at this time… Also inspected duct and dampers due to customer complaints about lack of air flow to the upstairs areas of the home..Found damper control levers loose causing damper. To close as system started… Based on findings I would highly recommend and automatic damper system to be install to better the air flow from system throughout the home…