What is this part on Peterbilt 379 by city horn

Tinkering with
My 94 379 and I found this air leak. The part in on firewall near the city horn. It got dark on me so I did not try and trace the air lines down.

it is wet in photos as I just sprayed it with soapy water.

 

That is what I was thinking as the exit runs up towards front of motor. Leaking pretty bad.

I’ll be able to see it in the morning a bit better.

thanks

 

Here is a short video

 

Looks like a filter attached to the solenoid. I am wondering if it is loose.
Looks like it has been on there for some years so I will more than likely replace it and the solenoid.

 

It was loose, however the plastic piece that goes through the filter and screws into the assembly was broken. So I just went and picked up a whole new assembly. Figure I might as well replace it all.