My 322 has started to run a little weird. It starts perfect, runs great for awhile and then seems to lower rpms and and shutter a little, keeps running but smells rich. Then it might snap out of it and run normal again. Almost like it’s not firing on all cylinders but still runs pretty smooth. Is it possible for it to almost go unnoticed with only 2 cylinders firing? Not sure where to begin, check plugs for color/ wear? check fuel pump?