Persistent lean condition - have literally replaced everything

[nathaniel2910]

I have had a similar or wll identical symptoms.
i tackled it head on and between head and carb manifold smeared high temp silicone sealant(automotive grade).
then the same for carbs to manifold and airbox to carb.
aswell as synking the carbs that did the trick, although it can still happen if the idle is too high.
id get the bike upto temp and reduce the idle to try and bring it back down.
could be a case of only one cylinder is firing untill warm when both kick in.