around 5-9 psi my car makes a sound which i can only compare to a flute. but under full boost no sounds and boosts to where i have my mbc set at 18psi, it makes no sounds with the n75 connected but that thing is not working properly as it startsboost at 5000 psi so i installed a mbc 4 months ago and had no problems till now. it just recently started happening in the past few days, the sound seems like its coming from the middleof the engine towards the drivers sidenot where the mbc is located.any ideas?
Thanks

 

You have some sort of leak. Unless you installed the mbc across the car, (or you have a rhd car), the sound should be coming from the passenger side. Check hoses for leakes and the manifold to turbo gasket, its a well known leak spot and could sound like this.