try not to get too worked up. these things can take a lot of tinkering around.
Signs still point to your issue being carb related. As Miki mentioned that needle needs to be replaced and based off those pictures you definitely should be replacing the diaphragm as well.
the best bet would be to order a full (and genuine) Mikuni rebuild kit for your carb(s) and replace everything. then pressure test and pop-off test again. While I think this will more than likely take care of your issue, at the very least you have 100% eliminated the carb as the issue if it does not (aside from tuning errors).
Signs still point to your issue being carb related. As Miki mentioned that needle needs to be replaced and based off those pictures you definitely should be replacing the diaphragm as well.
the best bet would be to order a full (and genuine) Mikuni rebuild kit for your carb(s) and replace everything. then pressure test and pop-off test again. While I think this will more than likely take care of your issue, at the very least you have 100% eliminated the carb as the issue if it does not (aside from tuning errors).