Update on the manifold stud. I thought it was done and dusted but just before the end of last year the noise after a long coast downhill came back. Upon inspection I could see the nut was missing from the same stud that was repaired last time and the end of the stud appeared to be missing. So after just over 1.5years the helicoil (which wasn't done properly by first mechanic) has let go which caused the stud to pull out a bit and the nut & end of stud to leave the chat.
So in the end I took it to my preferred Mechanic who had a thread doctor guy come out and remove + repair + replace the helicoil. Mechanic was able to replace this stud and 2 of the other ones also. Hopefully won't have to deal with the issue again for a while!
TSI Amarok engine/turbo noises-mani-stud-jpg