I have got this strange whistling noise that only happenes just before 0 boost i.e the engine not making boost yet. IT sounds like air being sucked through a very small hole but not sure where

Its not the same sound or pitch as the whistle the turbo makes so its not that.

We Took the Throttle off to clean it out becuase of low idle problem and when it was put back it makes this whistle noise. (it wasnt there before taking off)

I thought it might be the pipe that goes from the Aux Air Valve to the underneath of the throttle but checked the pipe and the inner sleve and they are both ok, so doesnt seem to be that.

Have checked all pipes and no splits or holes found.

Could it be the Aux Air Valve ? is there anything inside this that could make a whistle sound or could it be broken and whislte?

Anything else to check that could cause a whislte noise?