Surging

Go see what Ma Mopar wrote about how a carb works. The more you get the hang of the concepts, the easier it will be to figure out who is full of baloney. They may mean well, but they're just regurgitating nonsense or they've come to a conclusion based on a coincidence.

If you need examples of two barrel carbs on v-8s, look up the circle track classes that are restricted to 2 barrels. At one time there were mopars in the NHRA Stock classes that also were restricted to 2 barrel carbs. Just looking in the Mopar Performance Bulletin there's R/Stock, T/Stock, U/Stock, V/Stock. Not sure if that's still true, but again it wouldn't be hard to look up.

Here's an example where I purposely was testing on dyno with on just the two primary barrels of the carb. Overlay of Dyno runs 6000 rpm was not a problem. In fact the fuel curve was darn flat (which showed me that the secondary side needed tuning).

Three month old carb could still have a host of problems but some are more likely than others. Dirt, metal shavings left in passages or other manufactuing defects, old fuel that has left varnish deposits, using winter fuel in hot conditions. Start where the books always say to start, check fuel level. Look at the spark plugs, see if they have something obvious to show you.

I pretty much broke down the symptoms in my first post. You'll have to investigate to see which fits and then look for cause.

Trailbeast, I've had times when I thought backfire was fuel related, but there's really no reason for fuel to ignite before the intake valve is closed. So it pretty much always has to be timing related.