I once have worked a day long on an XYZ engine solving multiple problems all concerning carb tuning, carb pulse and engine manifold isues. In total about 10 of them IIRC.
After ironing out all errors, the engine ran like a champ.
So NO, I would not like to comment on possible issues for this problem. Give the engine a thorough overhaul with much attention to detail, taking nothing for granted.