I've noticed a wierd noise (sounds like an odd whistle) when the boost builds especially when putting my foot down. I've got a HKS bov fitted are they prone to leaking or is it likely to be somewhere else?

 

Do you have a boost gauge? Be the easiest way to tell!
Open mouth downpipe also causes a whistle?
Does it feel down on power? Have a look round the bottom of the intercooler and boost pipes for oil? Usually a sign of a leak

 

thanks will have a look for the oil. Unfortunately I dont have a boost gauge and dont have an open mouth downpipe either. Have to say it does feel down on power but it doesnt do it all the time, this morning seemed fine no noise or lack of power

 

I am suffering same problem, I have a gauge and no boost loss but can hear boost loss before bov dumps. Thinking maybe that's where I need to look?