Me and my girlfriend have some trouble with our 2002 A3 1.6.

We have a high pitched whistle sound coming from the top left of the intake or around that area (see photo).

I have checked the whole intake but canít find any visual damage and i have also checked everything i have found online like belts, tensioners and so on but nothing is faulty and the sound does not come from the belt area.

I have checked for vacuum leaks both visual and with gas and the idle does not rise anything so no leaks.

The sound is like when you blow on a gras straw or a piece of paper but it does not follow the revs and gets louder the higher the car revs. It gets louder depending on where you hold the gas pedal.
No throttle = no sound
Half throttle = high pitch
Full throttle = I canít stand it
When the car is at a stand still and i rev the engine the whine isnt as loud but as soon as i start to accelerate the sound depending on throttle position starts.

My girlfriends dad thinks that it can be a faulty exhaust manifold gasket so the exhausts can pass through a small hole between the head and the manifold. My bet is either the little cube i circled or that the first O2 sensor might be loose (i know, i know i should have tried to tighten it)

Has someone experienced the same type of sound from the intake? Does anyone have any suggestions?

I circled the area where the sound comes from in red.

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