Reply to "Delay Mechanical Ignition advance"

I doubt it's a due to a vacuum leak since that's the point of driving with the least vacuum. But of course any addition of air leans out the mixture. Worth putting a vacuum gauge on it

I also doubt the ported/non-ported vacuum advance could have an influence. As can be seen on the graph it's only at idle that the two differ. As soon as throttle position is above 10%, the ported port is subjected to full manifold vacuum.

I would still retest the advance at 1000, 2000, 3000 and 4000 rpm (with vacuum disconnected and plugged), be a bit scientific. Your neighbours will love you. Or come by, let my neighbours take the noise, they're used to it :-)