H issues

I have an H that has 2 problems that I posted earlier..had some time to work on some things. The H after it runs a few minutes (starts great)will start to throttle down a little, then throttle back up intermittently. Also, seems to have a miss, or labors from time to time. The miss isnt like an electrical issue, like a plug not firing, but more like a spell where the H seems to labor, almost as if the timing is moving then goes back. Here"s what has been gone over with the help of my farmer-diesel mechanic-all around repair man bro in law.
1.Removed dist. and inspected weights and springs, teeth, cleaned up, everything seems tight on the dist, shaft. Replaced points, cap, plugs, etc.
2. Set timing with light, seems to stay consistent when running in garage, but under load and working I get the rev up and down issue and strange miss issue.
3. Fuel tank clean, sediment bulb and filter cleaned.
4. Carb was rebuilt about 1 year ago and has been fine with no issues.
5. Same gas source for several years. Maybe an issue in gas?
6. Removed valve cover and observed running, nothing stood out, made some minor adjustments after warmed up.
7. Checked compression with engine cold and warm. All cylinders very consistent with very little variation between warm and cold and between cylinders.
8. Replaced coil.
9. Looked at governor unit, nothing appears broke, but I dont have much knowledge of this unit, just what service manual offers.

Sorry for the long post, just trying to post as much info as I can, any help is appreciated.

my H used to idle up and down by itself. ended up being a problem with the linkage between the carb and governer.

My H's governor spring was to lose. On my Ford it was the linkage as stated below.

Mine was doing that, found intake manifold gasket wsa blown out from loose manifold nuts.