Another rule of thumb

[Gelf VXR]

Is there a rule of thumb measure for increasing spark advance per AFR point?

AFR 13.5:1 to 12.5:1, would allow a 3 degree advance for example??

[SSpdDmon]

IDK - Some have argued extra fuel is essentially retarding the spark through burn rates. Personally, I'd try to find the best spark for a 12.7~12.9:1 AFR for N/A and 11.8~12.0:1 for FI and call it quits since they are known, safe "rule of thumb" AFR's. But, that's just me.