Here is an update.
I disconnected the vaccum line that goes to the top of the canister and connected it to a vacuum gauge. I read 10-14 in Hg. I put the vacuum line back and did a similar measurement for the line going to the other canister. The reading was the same. Is 10-14 in. Hg normal? Also, while measuring the vacuum, should I plug the vacuum opening on the canister and does it affect the reading? I left it unplugged. I can also measure the vacuum at other end of the hose, i.e. where it connects to the solenoid. Does it matter?
According to this post
http://www.n54tech.com/forums/showthread.php?t=13114
the vacuum should be about 26". However, he measures it by disconnecting the hose from the solenoid and connecting it to a gauge. I assume he leaves the solenoid vacuum opening unplugged while doing the measurement.