[WorkinLonghorn]

I'm definitely NOT a guru, but I've been running Q-jets only for the last 27 years and the only times that I've had a rich condition it was one of three things; 1) Choke plate not fully opening. 2) Air filter totally clogged up. 3) Float valve stuck open with some particle of crap. I would smell gas and see it overflowing out the vent. Fixed on side of road a few times.
Maybe there are other causes, but it wouldn't be the idle setting that causes massive soot discharge out the pipes IMO. Timing would not cause soot either. I've heard that too much pressure from the fuel pump might cause the bowl to fill up too high and cause a rich condition but I have no personal experience on this.
Did you set the float level exactly per the instructions? Jets are well seated? I like to fill the bowl while the carb is on the bench and see if there are any leaks but like I said, I am not very knowledgeable, maybe just lucky. -BA