Noise when accelerating

So since about 1 month my car has been making kind of like a jet turbine sound when accelerating under vacuum (when I'm boosting it seems like the sound was getting a little away) I thought it was a boost leak but everything was fine, no leaking till 14-15 psi (stock bpv probably and abs piping is ****)

Yesterday I started the car and it made a horrible noise. My friends says it sounds like a duck when I'm pushing throttle. This sound happenened in the beginning when the engine had a high load. What I mean by this is whenever I shift in low rpm (1500 to 2500) when the engine has a hard time accelerating this is when it makes the loudest noise. Now it will make a loud noise everytime. The noise seem to almost go away when the engine gets hot.
Noise is really loud when the engine is cold

So here is a list of what's wrong :
- Car is boosting normally to 7psi, but wont hold it very long and will go down to 4psi before I have to change gear (I don't know if this is normal but it is just a statement)
- Whenever I'm accelerating under 0 vaccum, I'm at something like -3 or -4 instead of the usual 0.
- My car will not go to it's usual 20 vaccum on the highway when giving little gas. It is like at 10 instead.

My thoughts are on a turbo gasket or something like that. Noise is really coming from the turbo/manifold part, front end of my engine bay.
People told me to check my manifold, and it's not cracked at all.

I'll look forward into lifting my car this week-end and check my turbo, if I find nothing i'll take it for a repair.

Okay for those wondering or coming here from google it was just a loose bolt under the manifold between the turbo and the manifold gasket. That's why I thought it came from the turbo, the bolt was rattling on it.
Still haven't found why my boost and vacuum is off, the car now boost only to 5psi and will go down to 3 til 7k rpm. I may try to add a spring on the wastegate to see if this causes the problem.