Well, after doing some searching on the web, I found this site: http://www.secondchancegarage.com/public/186.cfm
It confirms a poor idle mixture cause the needle to bounce between 13 and 17 inches, (scenario 15). The site also said that a high performance cam (I have a Patrick's 264 cam) will cause a lower base vacuum reading (scenario 3). Is the 264 high performance enough to cause a drop in idle vacuum? I'm going to rebuild the carter, and hope that all is well.

Any other ideas?

Thanks, Vince