The above is the best piece of advice you'll ever get
So many time I was told by the specialists "we'll investigate" and it meant changing things almost randomly or according to the fault code ( ECU, EGR, Air sensor, pumps etc) only to find the problem was not fixed and you are back to square one just with a lighter wallet.
Than I found an old fashion mechanic that eats breaths and s....ts diesel engines. Never went back to the specialist. He always tells me exactly what the problem/problems are ( or can be), shows me the faulty or broken parts once they are replaced.
Any car is only as good as the mechanic you know..... The worst are the "official mechanics" it's like comparing Mcdonald menu to Grandma's cooking.

