Problem with Mighty Demon 750

Still black smoke, or is it any better? is this in neutral? How far open are the 4 idle mixture screws? Are they open approximately equal amounts? If not, then some work on the primary vs secondary throttle opening at idle is called for.

Is the vacuum level under the carb still 13 in at idle in neutral and 8 to 12 in gear idling?

Any fuel dripping from the aux venturi's at idle? Look closely.

If you feel the idle screw settings are where they should be, try lowering the floats a bit. Idle it for a while to see that it goes down.

This is a pretty simple situation where it is all on the idle circuits. (Assuming the power valves are not open for some reason).