Hi Chris, I know this stuff for my '84, as I have to have it all in place and functional to pass smog here in CA.
Here is the vacuum diagram that I believe to be correct for a Federal emissions 1984.
That part is a vacuum switch and part of the original emissions setup.
I believe it is called the "TRC Solenoid Control Valve".
It controls or is part of the AIR injection smog pump control...
And here it is as my '84 should be...
That is a coolant controlled vacuum switch.
On mine is called EFE/TVS switch.
Here it is on my setup.
I have 2 of those... on in the thermostat housing, and another on the fwd part of the cylinder head...
The other is called the "Spark/TVS switch.