Duty cycle on the round connecter is pin 2 & 3. On the ubiquitous Sears meter, the red probe goes on pin 2, just the opposite of what one would think. The book says optimum is just a tad rich, or about 40% at idle and 2500 RPM. The guys are right, though, if you have a problem, trying to band-aid it with lambda tweaks will just throw everything off even more.

DG