Furnace precision tune up; clean and tune up furnace; clean burners, test ignition components, adjust gas level, test safety circuit, check indoor motors, checked all electrical components, tested indoor air flow, checked heating temperatures, and tested overall furnace operation. Replaced air filter. Furnace blower motor booster testing out of range. Replaced motor booster and operation. Due to age and condition of system, I would recommend starting to plan for replacement.