Diagnostic assistance for a Scenic 2

Hi, my wife works at CERN and suggested me to contact you. We have a Renault Scenic 2 from 2007 with the 1.5 dci engine, it has a bit more than 250K km. While on a long trip this weekend i started norticing that the engine does a wheezing noise when i accelerate strongly, noise which subsides when i depress the accelerator. I took the car to a garage in Prévessin who checked and said the turbo needs a replacement. I also think is is related to the turbo, but the noise is not strong and i am wondering if maybe this is more a matter of readjusting something, or even if it might be the normal noise of the engine… I wonder if you could help me double-check this diagnostic?