Suspected vacuum leak

[Wxneill]

I have a peugeot 207, 1.6, 110 hdi.
for the past year my car has been working great. Its had a couple turbo vacuum leaks in the hose from the actuator to the solenoid. This was fixed with a bit of brake line. i was recently on the motorway when i started hearing air gushing noises from the engine bay when accelerating. It still accelerates quick but not as quick as it used to.
Ive checked the solenoid and all 3 hoses coming off it, also checked that the actuator is getting vacuum and it seems to be working fine. Turbo still boosts fine but not as powerfull. Had a turbo inspection which passed. Ive also checked the pipes from the turbo to the throttle body and all the pipes to the intercooler. Theres no hissing noise under idle or when im driving slowly. When i feel the boost kick in, theres a loud continuous hissing noise until i let off the pedal, any ideas? Sorry for the para!