WTF is this vacuum line thing?
 

Can I cap off these vacuum fittings and run without this line? This thing with the white and green pill or whatever?

I lost the fucker at some point during my rebuild :(

Well news flash. I just found it. What the heck is the point of it? It looks like it has a one way valve on it.

As you suspected, it is a one-way checkvalve. It goes between the manifold plenum and the VICS vacuum reservoir.

edit: Just saw that you have an '03. My guess would be that it's the vacuum check valve for the VTCS actuator.

It's a float. In case you go fishing.

+1 LoL...Thats what I was going to say!

on a turbo car, i'd plug both ends and leave it disconnected.

after mazda recalled the ECUs and implemented some shitty "VTCS closed a lot" it sucks for turbo applications.