Arrived to do a performance maintenance. Set system for cooling. Measured the systems static pressure and found it significantly higher than the systems maximum rating. Measured a temperature split for cooling, and found the system cooling 21 degrees. Went outside and verified refrigerant levels. Verified operation of all electronic and mechanical components. Rinsed coil free of debris. Went back inside and checked interior of the furnace for cleanliness. Found bacterial growth present on the evaporator coil and heavy buildup of dust on the blower wheel. Spoke with homeowners about the system. Renewed the maintenance plan. Air conditioning system is operational at this time.