[101gav]

new to this site so hi all. I have recently took on a c30 d5 and am completely new to turbo diesels and would appreciate some advice.
After having the car a few days it began to make a blowing noise when you came off the accelerator, I took it to a garage who identified the swirl arm link had come off and that there was an air leak somewhere under the rocker cover. I returned the car to the dealer who tells me he had the swirl flaps replaced / repaired, although I have been unable to find out exactly what's been done so far. The car seemed fine for a few days I think but now intermittanly makes this sound, I can only describe it as a whooshing noise. There are no warning lights or loss of power. Is this sound normal for a turbo engine or should I be concerned? I want to try and find out before I go back to him in case it's normal and I end up looking a ****.
Any help appreciated.
Cheers