Stick with it mate , all modern diesels will carbon up with **** after running rough and being pulled apart.
We had Mitsubishi telling us we needed to spending $4500 on turbo and sensors to stop it going into limp mode
but a mate told me to clean the intercooler and induction pipes then give it a hard workout. (He also said to add a catch can to pollution lines but we didnt)
Anyway it only went into limp mode once not long after that and now it's been 3 years without an issue.
If the manager is truly on your side you will be fine, just get in it and see how many kilometres you can do in next few weeks.