Sure you don't have a couple injectors (service meters) plugged up. Working in dusty conditions like that fuel gets contaminated plugs filters and injectors. Does the engine sound like it's got a knock of any kind up around the cylinder head?

Wombat and Skinner, thank you so much for pointing me in the right direction! I got a little too close to a overhanging tree, and tweaked the stack spark arrester, pretty sure it caused a small leak in the pipe connection will check it out in the morning and let you know what I find. Thanks again for sending me in the right direction, this issue did not start until shortly after that contact with the low limb!

Try a new filter, if the other one was plugged so bad it will starve the engine of air lowering the power and make it smoke also. I would remove that tube if it's not factory.

Thanks Rome, removing tube and new filters on order, will not try to run it till they are installed. Our ground is not nearly as dusty as some areas are, the clay is very heavy!

Thank you Stevens, the engine runs fine if going down hill, sounds fine! Appreciate the thoughts cause it is easy to overlook something when up to your ears in it.

Is that one of these air cleaner contraptions?
 

Yes, very similar, but with a dry filter and tall stack on the air inlet, same crossover pipe!

Soot is definatly coming via that pipe. Problem definatly inside muffler, venturi not working. Common issue on agricultural machines. Cheers WF

took the exhust and intake apart, have turbo out to be inspected. A piece of the venturi section had dropped down into the bottom of the exhaust pipe, not sure if it caused any problem iwth the trubo, getting it checked out today. Anyone know where you could get a new venturi section of exhaust? Halton Tractor is no longer in business at least as far as I can find on the internet. Thanks for your help, Tom

Maybe you could use a pipe from a D6D, it would have the cone in it but have to have the exhaust elbow with the tube in it to hook the air cleaner ejector tube to.