Rust in blower compartment Gas valve unstable. It varies the pressure from 3.45 to 3.54 wci while running. Recommend replacement part but (second opinion) part v replacement is preferable as the system is 20years old. X air is high at 132.2 Removed, cleaned and installed gas burners Removed, cleaned and installed flame sensor Inspected heat exchanger Tested igniter Checked condensate trap Checked blower motor Checked and tested ventor motor Checked filter Adjusted gas outlet pressure to OEM spec