[Gaz64]

Can you hook up a vacuum gauge to monitor inlet manifold vacuum, while monitoring A/F ratio?

Then you need a really long slight upgrade where you can maintain a slowly decreasing vacuum level, increasing load.

If the vacuum IS above your power valve opening point when it goes rich, say 10 inches, then decrease your main jet to say 72, and retest.

If it has an A/F of 10.9 at say 14 inches, increase idle air bleed size by .002, and retest.