All Plugs Fouling on Right Bank

the only thing I can think of is the AFB. Either an air bleed is clogged on one side or the rod hanger is bent and not letting the rod set in the jet at the right height. All the plugs have been changed to new ones I assume. You may need to check the manifold also as said above. Smoke test or other. {you could actually use plastigage to make sure the gasket mating surface is even}. How about the valve adjustment? Just thinkin' out loud here. Good luck.