Carb "Water Valve" Help Request

[alice@domain.elided]

Hello guys,
This is a bit off topic.  My Scout has at least one "water valve" 
screwed into the intake manifold.  I have never really understood 
what this does, why it is needed, etc....

But now...
last evening, I was working on a Mazda pickup, when I broke off one 
of two plastic nipples on such a device.  Everything on this pickup 
is expensive, but before I pay $$$$ for a new one (or spend countless 
junkyard hours), I ask if anyone knows what these things do and, most 
importantly, are they necessary.  The broken device is called a 
"water valve" and apparently senses temperature of intake manifold 
water.  There are two nipples coming from it: one goes to a fuel 
vapor recovery carbon cannister (which I feel I could neglect/plug), 
the other goes to a fitting at the base of the carb (I think this 
enters the throat near the butterfly valve?).  And the device has a 
small filtered vent to atmosphere.  It appears a small air flow can 
be pressured through this device.

I have to screw something into the manifold water jacket hole.  
Can I simply plug the carb fitting as well and ignore the device?
The truck is an '86 with a Nikki carb and all sorts of hangon stuff.
I was messing around with the carb to figure out why it dies at 
idle. 

If you feel this inappropriate or too long, please email me direct.   
I will return to look this over today (Saturday) AM, so direct 
responses would help me most.  

Any help appreciated.  Really.  Mark