Hello, I hope the following is of assistance.
To start with check the basic items, fuel filter and air filter, replace these if you're unsure of the last time they were replaced, when replacing the fuel filter if possible check the quality of the fuel in it, any signs of metallic particles could indicate a more serious concern although it may be the filter is just blocked. Check that all the turbo pipework is intact, look for any signs of oil on the rubber hoses that can indicate a split, this would cause a lack of power due to no turbo boost.
The main thing is to make sure enough air and fuel are getting into the engine.
If possible have a diagnostic scan carried out on the engine management, this will retrieve any stored fault codes and assist in pinpointing a problem with a sensor or actuator.
As I said at the beginning check the basics first and go from there.
Let me know if I can assist further or if you have more questions regarding this and I'll reply as soon as I'm able to.