OK, I just took it out and had no issues with the shaking. But yesterday it was hit or miss (and more hit than miss)!

As for the vac hose, I did disconnect it at the distributor and plugged it for the test. The other end of the hose connects to a plastic thing (with other vacuum lines as well) on top of the front of the intake manifold (near upper radiator hose).

Shaking is only in gear, when I take it out, the RPMs go up and it stops shaking. Also, when i am moving along, it has no issues either. Car does have a tach which I confirmed yesterday with my dwell meter's tach function.