I have a sti 5 wagon that has developed a whistle on boost aside from a panel filter, hks ssqv and a centre decat and back box completly standard never had a whistle before.
Drove though some standing water NOT quickly but deep enough to have some steam out the vents, that night when i went out i discovered i have this noise, this whistle would appear to be from the passenger side so have checked the bov and the blanking plug which was replaced but still does it. Its not losing boost and holds it fine.
I am thinking possibly hose or as a mate suggested the y pipe under the tmic would this be the right line of thought?
Cheers guys jaymes

 

it's possible you have a boost/vacuum leak somewhere, best way to check is with the engine running, get some brake cleaner or easy start and spray it round each hose in turn etc and if the engine revs increase then the last place you sprayed is where it's leaking from.

 

i think its cos ur special

 

Ha seems kinda simple shall give it a whirl thanks for that jaymes