Peugeot 807: Specs, Review & Price

Hello everyone,

I have a Peugeot 807 2.2 HDi manufactured in October 2003 with 94 kW of power.

Problem:
"Some time ago, the timing belt broke, which resulted in a repair of the cylinder head. -> There is a lack of power at higher outside temperatures (it runs great when it's cold). Then, the mass airflow sensor and the turbocharger were replaced - but neither of those fixes worked."
Now I have this thing sitting on my property and I need to figure out how it all works. Has anyone here had something similar before and has any advice for me?

Sure, here's the translation:

"Thank you in advance."

Thomas.

Are the valve timings 100% accurate? Is the intake air path completely sealed? Is the boost pressure correct? Are the temperature sensors functioning properly? Is the injector return flow within acceptable limits when the engine is hot?
Does the fuel pressure remain within its limits even when the engine is hot?
I'm not very familiar with French people in general.