Becky,
The original pressure guage that I borrowed was one that was purchased from
Medela and it tests the Classic right at the connection to the pump, not
through the breast shield.  When I wanted to test pressure on the Lactina and
began to play with the guage, the only way I could come up with testing was
with the rubber stopper - through the breast shield.  You have made an
excellant point!  With the pressure guage I am no using I still test the
Classic directly and the Lactina through the breast shield.  Perhaps that is
why I see different pressure.  Tomorrow I will do some testing using the breast
shield on both pumps and see what happens.  I'm just too tired to try tonight.
Keep tuned - I'll be back with the rest of the story.

Yaffa Stark, MA, IBCLC