Since you asked, I shall.
The tech and I both ended up feeling pretty foolish.
Our tech called the Deere dealer to price a new or rebuilt injection pump. I don't remember the exact cost, but it was pricey.
Anyway, we buy a lot of parts from this dealer, so they know us and are willing to offer helpful advice.
The parts guy suggested from what our tech told him that someone had put gas in the fuel tank.
Now, the users swore that they hadn't put gas in the tank, nor could you smell any gas in the fuel, although the scent of diesel would likely overwhelm that of gasoline.
Anyway, our tech drained the fuel and put in fresh diesel.
After it worked through the residual of the old presumably gasoline contaminated fuel, the thing ran like a champ again.
Just goes to show you that it's often something simple causing a problem.
Had the users told the truth, and said that they had accidentally added gasoline to the fuel tank, the issue could have been resolved quickly and easily.
That's okay, since I know who was supervising the operation of the equipment on that day.
They don't have a whole lot coming from me or the tech for the foreseeable future.