Thank you. I did read that the clunk noise can have many different causes. I guess the car needs to go in the air to figure that one out. I did go ahead and ordered this product: https://frenchysperformancegarage.com/collections/nissan-skyline-r32gt-r/products/fpg-bnr32-attesa-high-pressure-hose-replacement-with-optional-pressure-sensor-adapter-fpg-116?variant=42829932724402.
Since I am quit sure that the leak is coming from the Attesa hose. Also it might be leaking at the Atessa pump above the read diff, since I do get a bit of oil leaking from the right side area of the rear-diff, also red colored oil.
Is it harmful to drive every now and then with the car with this small leak?