Sounds to me like you have checked out the problem in a logical way. First, carb and fuel/air supply. At one point even changing the carb completely only to be left with the same problem. If it was air/fuel supply, the symptoms would have changed measurably even if the problem remained. So, assume it is NOT the carb...

Next logical thing to troubleshoot is the electrical system. You replaced the coil, reg/rect, spark plug, leads and pretty much everything else in the ignition system. This also made no difference at all.

As the problem occurs in the rev range when ignition advances, anything that controls advance could be the culprit.- TCI and also the sensor in the front of the stator. Many TCI/CDI systems have 2 circuits (one for retard and one for advance) rather than an actual curve, so there is one possibility (dead advance circuit in TCI or the sensor which is part of the stator). Me - I'm too dumb to bench test a TCI so replacing it with a known working unit is the best option.

A left field suggestion...
1. a rat may have crawled up the exhaust pipe and died. It's amazing how much crap a family of rodents can pack into an exhaust pipe. This will have the effect of reducing the amount of exhaust gases that can leave the system and has a similar effect to limiting the air inlet. This happened to me when I restored an old Yamaha XS750 (with straight-through pipes). Had me absolutely stumped why the bike would not run. Took of the pipes and extracted about 10 litres of "rat house" from the straight-through pipes. After that the bike ran flawlessly.