Could it be an improper jetting due the change of the combustion chamber by milling the head, because, when I turn my gas cup off, the engine begin to idle correctly ?!?
I only have few mods like : Pro Circuit pipe, Boost bottle, open box with K&N, timing +4, and head milling. My main is a 280, my pilot is a 27.5 , Elevation is 78 M (256 ft.)