DCM1 complete; Heat; (1)F16251 replaced. System is functional. All components are operating within manufacturers specifications. Gas pressure and temperature rise are within design parameters. Heat checklist attached. Blower wheel is extremely dirty, however pulling to clean would be difficult due to location of existing gas line. Ductwork has issues. Some vents where you would expect returns are actually supplies, some vents you would expect supplies are actually returns and one supply isn’t hooked up Filter was extremely dirty and green mesh located in main return could/should be removed