make sure carbs are sync. you have crossover tube on carbs? you can try 30 pilot/280 main. Turn air screw in one full turn to see if it helps
Try one suggestion at a time and test. Don't do all these things at once thinking, its gotta be fixed now.
If you pull carbs, the reed cages are sitting in the cylinders, pull those out and check your reeds for breaks, cracks and they should be closed. the reeds should be resting on the cage