Good afternoon,
  I can't believe that I'm stumped on this one but perhaps we could have
some light shed if possible...

My 95 S15 Jimmy used vac actuated blend doors, transaxle switching, etc.
It's the system with the vac 'ball' under the hood.  Here's the question -
where do check valves fit into the vac reservoir equation?  I know that the
reservoir has an inlet and outlet and one side has a check valve.  I had to
cut the 'bungs/tees' off my reservoir and replace them with a shadetree
solution (I used brake bleeder screws into the retapped plastic).  Anyway,
the bleed screws work like a charm but I think I cut out a check valve so I
wanted to know which side I should add one to.  I have no 4WD currently and
my blend doors are a little jacked up (I figure for certain this relates to
a vac issue - more than likely as a result of the vac ball mod).

Any thoughts??

Thanks!
Andrew.