Actually according to Lycoming calibration specs., an IO-320 (160 HP) at rated power uses 75 to 76 PPH fuel flow that's about 12.5 GPH. Before you cover up a high CHT condition by dumping fuel at it, check the fuel air ratio the fuel control is delivering to the engine to see if it is indeed lean. Fly at 3500 ft, set 24 square, lean until one cylinder peaks EGT and record the peak EGT for that cylinder. put the mixture back full rich, let the EGT stabilize then record the full rich RGT for the same cylinder. If the difference between peak and full rich is 185 to 230 degrees F then the fuel air ratio is in the correct range for your engine. Putting a richer jet in the fuel control will only make the engine loose power, and can actually cause premature wear on the cylinders.