whistling sound under boost

[triplej3]

going to give this a bump, still have an issue with a whistling and boost. in 5th gear on the highway ill peg it to 22psi, will whistle loudly and the car wont hold boost, it will get to 22psi wont hold it and drop back to 14psi and wont boost back up higher then 14-15psi

things iv done so far

fix airbox leak as above, done turbo manifold gasket (gasket looked healthy too) iv checked hoses top and buttom example n75 to wastegate lines, vacuum lines etc they all seem healthy, today im pulling the front bumper off the car to check the intercooler piping (airtek intercooler kit)

[sambb]

To be honest if its hitting 22 psi peak and then drops to 14-15psi afterwards, I'd call that pretty normal. A K03s isn't going to hold anything like its peak boost throughout a pull.
I'd be looking at the boosted side pipework eg turbo compressor to intercooler to throttle body. Look up 'inlet boost leak test' on vortex and you'll find how to do that. That'll definitely whistle under boost. Or check the turbo to exhaust flange too. To check the hot side gaskets you can use the Subaru top engine clean/seafoam method and be ready with a torch to look for escaping white smoke. Doesn't always work but will reveal a bad leak.
You may also remove and check your diverter valve. I wouldn't have thought you'd even hit peak boost with a shredded diaphragm but it could be a worn out base seal on the piston and its just not able to hold max boost without spilling over. Unlikely but possible.
Really audible whistling under boost though.... my odds are on an air leak to atmosphere somewhere.

[triplej3]

fixed it

tightened and adjusted all clamps and hoses on the intercooler, tightened up the sensor thats on the bend off the throttle body hose was able to use two nuts to get it really tight. all seemed quite good as it was. throttle body hose was slipping from the bottum but not by much, brought a more heavy duty clamp for it. didnt find any split hoses or damage so not sure just happy it doesnt sound like a referee ahh =p

samb thank you