Performed semiannual maintenance on two liquid propane furnaces. Inspected all Performance, Mechanical and Safety systems. I did note that both systems are running high static pressure above the manufacturer rating. However, due to how the attic was spray foamed after the installation of the HVAC systems, without removing the spray foam lining and cover from the furnaces, there is not much that can be done to help with air pressure relief. I did change out two 16x25x4 air filters at the filter bases. Everything is working at this time. Did reset filter and service reminders on the controllers inside the home.