Furnace clean and tune. Cycled system. Checked heat exchanger, found some rusting in heat exchanger. Checked flame sensor and burners, ok. Checked igniter, sowing signs of wear, but ok. Checked and adjusted gas pressures to maximize efficiency. Checked for CO and XS air in exhaust, normal levels found. No CO found in airstream. Found ventor motor noisy with signs of heating ware. Recommend office to check on warranty and replace under warranty. System is operating normal at this time. Job complete.