sensors in thermostat housing?

[Little Brother]

I did an engine rebuild this winter and am reassembling everything, along with de-computerizing the car. My question is this: The factory thermostat housing has two sensors that scree into it and each has 2 - 3 wires and/or vacuum lines coming from it. Sorry I don't have a picture handy, but can anyone tell me what each of these sensors is used for?
Thanks!

 

[gedmeyer]

Ecklers catalog lists them as: EFE Control Switch and EGR Vacuum Control Switch.

I'm pretty sure these are the ones you are talking about.