Has any other work been done?
Are you sure that you got all of the old gasket removed from the return tube, it is not easy to see even if you have a lift.
Did you check the top oil feed banjo bolt for being tight, it can leak down over the return pipe.
Is it an active drip while the engine is running or just pooling after parking the car.
We had 1 or 2 5cyl over the years that the turbo oil feed pipe or solder joint at the the turbo inlet banjo area was cracked and leaking oil.
It is not easy to diagnose an oil leak in that area with out engine oil dye and a lift.
You can remove the turbo top heat shields for better access and investigation.
Dou you have an oil burning type smell after parking the car, if really a bad leak do you see oil smoke?
It is tough to diagnose unless we are there.
If possible send pics of leak area.
The angle gear needs to be removed to access the flat gasket at the turbo. When you say you did this twice, you removed the angle gear each time? Trying to gauge the scope of the repair and what was actually done.
While replacing this gasket, it is also recommended to replace the "o-ring" seal at the block at the end of the oil return pipe. The angle gear definitely needs to removed to manipulate the oil return pipe into the block with the new seal and align on the turbo side with the new gasket.