Exhaust blowing noise

Hi everyone I’m needing some help if possible cos I’m at my wits end. Had car in at Skoda main dealer and also two others because of a blowing noise when I let off the accelerator. First I though it was the flex so had I check they said definitely coming from higher up, had car in for service at dealer and asked them to look but they couldn’t see anything and recommend I should book it in a diagnosis at a cost of £96 for the hr, came back with we’ve been out 2 miles in it and also had it on the ramp but can’t see where it’s coming from so I requested my money back. Had it at my local and they said I could be the turbo to manifold gasket so I said ok do it but it’s still got this blowing sound. The car is a 2010 Octavia mk2 fl vrs tsi, anyone else had this issue that could shed some light on this for me.