I have a 1990 dodge b-250 318., I just cleaned my throttle body. I was smart enough to do a little video around the whole thing before I took it apart, but apparently was not smart enough to save it properly..... Anyway, its all put back together but this component (in the middle with the purple and green wires) has a vacuum nub on it, and I cant find any loose hoses, and cant figure out what it even is, or if there was ever a vacuum line attached to it at all. The component is self contained, and only has the one vacuum port, and the electrical connector. Is it a vacuum sensor, maybe?

 

Ive never had a TBI Dodge, only Chevys But here is a pic of the TB...It looks to be the same or similar..
To me it looks like you are looking at the MAP sensor..where there should be a hose on there going to the intake??? Maybe??? (see bottom right pic)

 

I think that lines goes to the base of the throttle body.

 

Oh yea..,you are right...the other end is in the top left-hand pic

 

That looks like the part, but all the vacuums on the back of the throttle body are accounted for.... Hmmm. I'll look at it again tomorrow. something is routed wrong. Its running fine though....