diagnosis aside, I might shoot for "all in" by 2800 or 3000 and then use an adjustable vacuum canister to add an aggressive advance during part throttle cruise. That low stall speed converter (although OK for the combo) will maybe like the advance to start a little later. With that cam there is plenty of low end cylinder pressure so you don't need advance that early. The 2.73s are also a good reason to keep the advance curve later. You'll be spending a lot of time with your foot in it in the sub-3000 RPM range.
I don't think that the advance curve is too aggressive that it would be causing a lean enough condition to pop through the carb. You would have crippling detonation long before it got that lean. It may be a combination of lean mixture and too much advance, but advance alone isn't the problem there.
My suggestion is to readjust the secondary air doors. They have a spring and two set screws on the air horn. It sounds like they are slamming open causing enough of a lean bog that its popping back. My Qjet has no secondary lockout cam for cold operation and if I open it up too soon before its warm, look out hoodliner. There is a flathead set screw on the side of the airhorn near the pivot shaft of the secondary air doors. Then up underneath that set screw is an allen head screw. Loosen the flathead set screw and turn the allen screw in by half-turn increments and see if that helps. Over time the spring in there that resists the secondary doors gets weak and lets it slam open. Tightening that allen screw puts more pressure on the spring.
You can also double check the vacuum brake for the secondaries. If its not operating properly it won't allow smooth operation of the secondary doors. Just push it in by hand, stick your finger over the hole and see if it stays there. If it moves, replace it.