vaccum flow direction question
 

Part No. 6 in below diagram is a one-way flow do-hickey; came off in my hands while doing valve cover gasket. I don't want to learn the full functionality of the vacuum system, I just want to know what direction the air flow is so that I can place it correctly (had to replace the vacuum lines; they fell apart). Would appreciate if somebody could inform me! One side of the part is black & what side is white; it works presumably since I can blow through it in one direction but not the other.

The vacuum source is the intake manifold so it would have to flow "into" the manifold if you want things to work.

Picture I found on Google
http://lh3.ggpht.com/_86lz7nzpGDQ/S7...lve%20copy.jpg