Could you please provide a more detailed history.
Is this tractor new to you of have you had it for a long time?
How many hours on engine?
Did this condition happen suddenly or slowly over time.
View attachment 102852
Has any work been done on the upper part of the engine where cylinder heat and injectors were touched?
Is your engine turbo charged?
Where do you get your diesel fuel? Big truck stop or small service station?
Check air intake system for rodent nests which will restrict air into the engine.
Dave