Today I did all the things that were suggested...
I swapped the carbs front to back, and guess what... it didn't make a difference. The front cylinder still sputtered and popped and backfired, etc. The good news, is that this tells me that I'm capable of cleaning a carb out just fine, and that I'm not crazy thinking that it's spotless and perfectly operational. Just for kicks, I swapped the coil packs and intake boots at the same time, and nothing had any effect on the condition.
Knowing that its not the carbs, I put the bike back together, then started at the other end. As suggested, I checked the pipes for dents/kinks/cracks all the way down, and (as I already knew) there were none. I removed both cats/silencers, and fired the bike up. Good thing that I had my Remmington headphones that I use for trap shooting on, because man that sucker was loud running on open headers!! (my neighbors must love me)
The good news, is that I can also eliminate the cat/can's from being the problem here, since the backfiring and poor running condition remains the same with or without them. Just for kicks, I swapped sides when I put them back on. The bad news of course, is that if the problem isn't being caused by anything on either end, then it's somewhere in the middle... which is always more difficult. At least it's getting chased down a bit.
FWIW, after the engine warmed, I checked the oil again, just because, and it was perfectly full to spec.
So... if it's not the carbs, not the cans, not the manifold boots, not the coil packs, the valves are within spec, and the cams are where they should be, what's next?