Pro, You cannot enrich the mixture without getting a code. The tolerances for the rich and lean are so tight that the slightest adjustment will give you codes. When Yale made the switch to the emission controlled engines all the programing was set to tight. You might be able to get an after market ECU that would allow you a wider range of adjustment. I have not tried this and not sure it would work or if it would be compatible with the current system. Good Luck.