I am very familiar with the too lean one. It would happen when my MAF screen would decide to occasionally work it's way loose and turn partially sideways. Eventually gluing it in place solved it.
"Fear is a feeling, not a barrier." -me, 1998.
2006 Impy SS, LS4 transportation appliance 100K (Ultra-flo's, spacer, CQL rockers, DRB, etc).
1996 Fleetwood Brougham LT1 101K.
1995 Caprice 9c1 LT1, 238K (in more than one piece and being parted out)
1985 Honda VF1100S, for those days when you just have to crank off an 11 second quarter-mile. 22K