As you mentioned - beware for people wearing glasses.....
Here's the circuit pictorially....main picture with coloured cooling pipes compliments of EC.

Excellent about the oil and the dust/dirt build up....certainly justifies the catch can - although, (possibly covered years ago when the catch can was getting "kicked around") ....wouldnt the teflon coated screw impellers need a little bit of lube for longevity and as an aid to seal and reduce tolerances that fraction more? = more boost and longer life???

Now we need to divulge a solvent we can spray into the intakes post the air filter (possible Y-pipes) to dislodge and flush to prevent the remove/install - but at the same time not causing any unnecessary problems with the motor. Possible atomised fuel injector cleaner - as long as it's okay for the MAT and MAP and the teflon.