First thing I would do is assume you have a blockage, which is common on VW/Audi motors at the oil pump pick up tube. Take a look under the valve cover after you've removed the oil fill cap, it might be difficult to see because of the oil baffle. Does it look like there's a bunch of black jelly on everything? If the cams, journals, and inside of cylinder head aren't shiny, and have turned to a dark brown color, than means the engine has a sludge problem. If that's the case, remove the oil pan and check the pick up tube.