If they are both vacuum secondaries, you probably have no pump shot to the two rear barrels on TWO carbs. This would create a much amplified dead spot that is typical of vacuum carbs when not tuned correctly. It would be magnified with the large plenum area of the tunnel ram. My susgestion would be play with the shooter size ( squirter size ) on the primary side of both carbs. make gradual changes.

When it's close you might try to fine tune it with the pump cams. Do the same for the back as the front. I have heard that some folks running vacuum secondaries on tunnel Rams stagger the vacuum springs by ONE color so that they come on somewhat progressively at slightly different vacuum levels in an attempt to not "shock" the engine with a large intake of air with no pump shot all at once.

Good luck.

JS