You will probably be able to improve your results by upgrading your oven with new or refurbished catalytic emitters and perhaps adding some zoning.

Gas catalytic emitters rely on a platinum catalyst to oxidize the gas. After a period of years, the catalyst can migrate causing hot spots and cold spots across the face of the emitter. Because these "flameless" emitters do not glow, this problem cannot be detected by the naked eye. You can use a hand held infrared thermometer to take temperature measurements across the face or use a thermal-imaging camera to detect this problem. If you find that your emitters are no longer uniform, you can replace them with new units or have them rebuilt.