Originally Posted by SoguRacing

ok, do this, add a bottle of isopropyl alcohol to about a half filled gas tank, drive it around a bit to get it mixed and in the fuel line. alcohol lowers combustion temperatures thus NOx levels will be lower. also, nox resolved from running lean which is one of the symptoms. get the highest percent isopropyl alcohol and try again, get around 90% because the other 10 percent is water, though water is not combustable, it will dilute enough to not cause any harm. also, try retarding your timing a few degrees. that may help. these are just cheap/money free possibilities. the alcohol wont hurt your engine, just dont use more than 1 bottle..about 16 ounces

Let me know if this works for you. i bet it will. pm me or something