What is this??
 

I have attached a pic I found on the web. The thing in the red circle is attached via some linkage to the throttle, but on my '82 300TD this thing is not connected to the linkage seen below. Can anyone tell me what this thing is and do I need to get it connected?

That is the servo for the cruise control.

So I guess my cruise doesn't work...Is it a problem to leave it unconnected? Does anyone know if any reason why it may have be unconnected in the first place. This car is new to me, I am trying to figure things out as I go.
Thanks.

I am not aware of any problems- 2l of mine are non-functional and disconnected

usually the cruise amp under the dash goes out, and it's difficult to get replacements, so most just disconnect it when working under the hood, and never hook it back up. you can open up the CCA and re solder the connections, but it's a crap shoot.