I have the same carb, mine did not come with any restrictions on the IABs on the primary side. Square jetted at 78 out of the box it pinned my wideband at 10:1 (lowest it reads) at WOT. If you've got more jet I would suspect you are way rich at WOT if yours is of a similar vintage to mine and has the same calibrations. 74s or 75s square was a much closer starting point for me with the stock passage calibrations, still way rich everywhere except WOT though.

I would go to 78 square and see what that gets you. With 78 square this carb will cruise with an AFR of less than 12.0. What is you current jetting? If you are at 86/82 I'd suspect you could be on the verge of a rich missfire.