Thanks guys. I really don't want to give up the additional advance that I am getting at idle, helps with cooling, etc. Connecting to port vacuum will only make the can operate at cruise, which is where I am currently having the issue. Either way, to your point, I am going to fool around and see if disconnecting helps, that will at least tell me it is an ignition timing issue and not a carb issue. The vacuum at idle is stead and solid 19-20", so no worries of the timing jumping around. The car jumps to life off the starter (starts really easy), and now with the cooling issues solved I am feeling better about everything.

Is there a way to limit the advance from the can? I know you can adjust the "on off point" with an allen wrench, but is there a way to limit the amount of advance?