What's this part? Booster Reservoir?
 

Hello,

In the picture below, I know the white fitting going into the brake booster is the check valve. Is the black piece a vacuum reservoir?

https://cimg9.ibsrv.net/gimg/ls1tech...4cf163b822.jpg

Might be some form of vapor separator to prevent gas fumes from accumulating in the brake booster.

It's just some kind of filter, a lot of GM cars from the late '70's to mid '80's had them, we always took them off and threw them away! LOL! It doesn't hurt anything not to have it.

OK, thanks guys. I was able to add the term filter to my search and it came up with results. Apparently it filtered contaminants from entering the booster as G Atsma suggested.

Unless you're trying to hook up a hose and use the booster as a fresh air supply i think you'll be fine with no filter.