k04 question please... what is this?

ibiza_95

1.8T MK2 Conversion
Ive plumbed my k04 turbo in,
oil feed, oil return, water in, water out... now on the back of the turbo ive found a threaded hole with a tiny hole in the back of it, cant see where it goes to but i took a photo so you could see... as i understood there were only 4 lines to and from the turbo so what is this one?

5f5agx.jpg


2mgowom.jpg


Also...
Do i NEED to run a secondary water pump with the k04? i heard you must use it or itll bake itself but not sure how true this is?

Thanks in advance
 
SWANSWAY CUPRA Dealership