Dont worry about the plugs getting fowled around 13:1... that only starts to becomes an issue if you are idling so rich there is black suit coming out of the tailpipe, if you are idling at like 10:1
2016 WRX STi Limited (current)2001 A4 1.8tqms (donated)1991 GVR4 #1933 (sold)old.dsmregistry.com/detail.php?carid=218 (dismantled)