I did not get a good idle with ported vacuum to vacuum advance canister. Not enough timing at idle. I had to run FULL VACUUM to the vacuum advance canister to get it to idle. I run 12 degrees at the crank with the vacuum line plugged and 800 rpm. As I raise engine rpm to around 3000 rpm, I get timing of 32 degrees. I then plug in vacuum line and my timing goes to more than 20 degrees (not sure so I wont say) but when I raise engine rpm to around 3000 rpm, I get timing of 52 degrees.
http://www.lbfun.com/warehouse/tech_...t%20Timing.pdf
http://www.lbfun.com/warehouse/tech_..._explained.pdf
http://www.lbfun.com/warehouse/tech_...ance_Specs.pdf
I've included a couple of links from Lars Grimsrud and the last link states if you have a radical cam and need more timing to get an acceptable idle, use manifold vacuum to your vacuum advance. I also changed my vacuum advance canister to the AR31 can and it made all the difference.
Read these links and do what Lars, Camaro, and I say and this will cure your motor.
Good luck and keep us posted.