OK so here's the update:
I couldn't unplug the breather tube. I suspect its loaded with rust and grime at the end near a 90 degree bend in the tube. There is another 90 in the tube, so it could also be plugged up there.
I had some extra air hose left over from my Airlift 1000 install a couple years ago. It fit right in to the hose coming out of the diff. So I lubed it up and inserted about 1.5", and put the hose clamp back on the joint. Zip tied the hose to the clips the tube used to be attached to the frame with, and voila! problem solved.
Anyone out there think I need to go further? IE is this the permanent fix, or should I still either unplug the tube or replace it?
Here are some pics:
https://plus.google.com/photos/10428720 ... 4060727601