Hi I am doing a head gasket and I remove the air duct between the mass air sensor and throttle control housing. Inside there is a small amount of emulsified oil. I discover it is coming from a tube that, looking from the throttle side of the 90 degree solid plastic bend is the first to enter the bend and goes towards the top of the engine where it bends 90 to a junction, which then passes into a box located side rear of engine between the block and head level, below the inlet manifold. ie it is not the idle air control hose but the one next to it.
I do have a probable blown head gasket. Should I dismantle further along the contaminated pipe?
Where could the oil be coming from?
This box I have found what is it?
Is this system to do with vaccum?
Thanks in advance

car 940se 2litre 1991