There is a good webinar at www.eaavideo.org.

20% excess fuel results in about 3% increase in power or (1.5% increase TAS). This would be your best power mixture about 75-100 deg ROP.

20% less fuel results in about 10% loss of power or (5% decrease in TAS). This would be your best economy mixture 30-70 deg LOP.

FWIW

Jon