Complete 1 system furnace repair and preventative maintenance check. Put in a washable filter at the customer's request. The filter is causing high static pressure. Recommend breathe easy electrostatic filter for improved static pressure and particle filtration. Dusted out furnace cabinet. Cleared barometric tubing. Tested combustion and found safe carbon monoxide levels and good oxygen levels. Tested mechanical and electrical components, all in good shape. Recommend surge protection to protect the furnace from power surges. The system is heating normal at this time.