The fitting that screws into turbo that the oil feed screws into
what size hole should be in it?
Mine has like a 5mm hole but some of my m8s cars have a smaller hole
about 2mm...

I'm just wondering that as mine still has the oil feed from the head if it would be ok to put on a fitting with the smaller hole and would this increase the oil presure at all?..

As the smaller hole would give a restriction in the oil flow