2.5L vacuum parts

[CheepComanche]

There is this part on my 2.5L 1989 that I haven't been able to find any information on. It has two vacuum lines going to it. One of them supplies vacuum and other one goes into the air box. In the air box there's this little piece of plastic that has another vacuum line coming out of it. Which then goes into a check valve and finally to the pre heater hose. This all seems extremely complex as my friends 1988 4.0 has only one vacuum line to open the pre heater. Any insight is appreciated 

[eaglescout526]

Dammit. I used to know this one. 

I honestly have not really noticed the thing function. I can speculate it’s something similar to carb set ups where it’ll hit a certain temp and open up to allow vacuum to pass through. Like how it’s lined up to the preheater hose. 
Course I live in the desert so it’s probably always open haha. Or closed. How ever it functions. I know the 4.0L air box has the same exact thing in the top of its lid. 
 

Let me do some digging in my literature and see what I can report back with. 

[Ωhm]

Not sure how I came across this, but is this your setup?

 

Thermostatic Air Cleaner (TAC)

 

 

 

[CheepComanche]

4 hours ago, Ωhm said:

Not sure how I came across this, but is this your setup?

 

Thermostatic Air Cleaner (TAC)

 

 

 

That's exactly it. So there's two thermal check valves?

[Ωhm]

4 hours ago, CheepComanche said:

So there's two thermal check valves?

 

IDK. It does seem to be so, but one is call a TAC Sensor while the other is Thermal Check VLV. Both must switch vacuum, I think.