Hey, I found the part number. It's 73711FA000, superseding 73710FA020. I'm not sure what it does with the vacuum, initially I thought it was part of the pulsed secondary air injection system to clean up exhaust emissions, but that one looks has a little filter hat on it. Here it is on the official website - https://parts.subaru.com/p/49283327/73711FA000.html
For some reason it's listed as part of the air conditioning system and part of the A/C diagram, despite being connected to the intake manifold. It's not listed on any of the vacuum routing diagrams as far as I've seen, which is why I think so many have had issues finding it.