On my car, you measure it either at the EHA (with a harness) or at X11 (+ to pin#2 / - to pin#3) fully warmed up.
At X11:
You should get a fluctuating duty cycle (fixed is a fault).
50% fluctuating = stoichiometric
Lower %'s indicate leaning of the base mix
Higher %'s iindicate richening of the base mix

Was that your question?

__________________
-Marty

1986 300E 220,000 miles+ transmission impossible
(Now waiting under a bridge in order to become one)

Reading your M103 duty cycle:
http://www.peachparts.com/shopforum/831799-post13.html
http://www.peachparts.com/shopforum/831807-post14.html