Pkg clean and tune. Furnace. Cycled system. Checked heat exchanger, ok. Checked, removed, and cleaned burners and flame sensor. Both are ok, checked electrical connections and clamps. Checked and adjusted gas pressures to maximize efficiency. Tested for CO and XS air in exhaust. Found XS air higher than normal in exhaust. Adjusted gas pressures down slightly to lower XS air levels back within range. CO levels in exhaust are normal. No CO in airstream. System operating normal at this time. Ac. Cycled system. Checked and cleared drain lines. Checked and cleaned electrical compartment. Capacitor and contactor are in working order. Compressor and fan motor tested ok. Used coil cleaner on condenser coil. Hooked up gauges and checked pressures and temps. Indoor coil tempmwas 39. Subcooling was 11, indoor cooling was 17. System operating normal at this time. Job complete.