Governor linkage looks good, including spring. I really don't think it is the governor because it isn't simply bogging down, but starts running rough as if one cylinder is dropping out. If I stop moving, within a minute, the engine will smooth out again.
I just pulled the heads off today and #1 has a lot of black carbon buildup. Later today, I am going to remove the valves to verify that the seats look good or if they need lapping. While it is apart, I will replace the hydraulic lifters, head gaskets, intake gaskets, and exhaust gaskets. I read in the forum where someone said the lifters can cause this sort of thing and someone replace them and the problem cleared up.
