Really weird ignition issue...

Having vacuum to both the timed port and manifold port sounds to me like the butterflies are open too far to get it to idle. The secondaries aren’t fully closed at idle by chance are they? If not, my thought process is it needs more timing at idle which will allow the idle screw to be backed off getting out of the timed vacuum port. We installed a “340” cam in my dad’s 318 with electronic ignition and if I remember correct we set timing at 14 degrees btdc. These are just some ideas of how I’d look at it.