Since I have owned the car there has always been a small amount of oil near the join between the transmission and engine. I had feared it was the rear main seal but when I dropped the transmission for the clutch job, the seal was completely dry. I then attributed the oil leak to the turbo oil drains.
After replacing the turbos and fitting new seals I found the leak was still there, and getting worse. Only possible explanation would be the oil pan gasket. Luckily the parts are cheap, but its quite a time consuming job.
Unfortunately I did not have any power steering fluid in stock, so I did the job with the subframe hanging loose and the steering rack still attached via the hydraulic lines. This was a huge mistake and makes the job very slow, there are many many oil pan bolts to access and on jackstands its a slow process accessing them all getting in and out under the car.
I cleaned up the oil pan, which turned out great, at that point the job was going very smoothly. The aluminium bolts for the oil pan require 8Nm+ 180 degrees for the long bolts and 60 degrees for the short bolts. Unfortunately I miscalculated the amount of angle and over tightened several bolts until I realised. This meant the bolts had to be thrown away, and because this is such a critical gasket, I elected to throw that out too. Luckily
Socket had a spare oil pan gasket kit, so I used that kit to get my car back on the road the next week. Overall not a fun job at all.
Suggested strategy for doing oil pan:
Remove microfilter cowl
Remove air filter, charge pipe and lower charge pipe
Remove fan
Unbolt coolant hard pipe from subframe
Remove steering linkage bolt closest to firewall
Remove screws for front inlet pipe, pull inlet forward for access to belt tensioner
Loosen tension on belt and remove belt
Jack up car
Remove undertray
Remove sway bar
Disconnect steering shaft from firewall
Unbolt steering rack from subframe
Drain engine oil
Remove 4 bolts to engine mounts to the subframe
Unbolt power steering pump (this bolts onto the oil pan)
Support engine with engine brace from lift point
Unbolt front subframe and lower onto blocks.
Undo all bolts for oil pan, clean all surfaces
Install oil pan, torque all bolts to 8Nm
Apply 180 degrees to all the long bolts, 60 degrees of rotation for the short bolts.
Reassemble engine, refill oil. Additional steps are required for automatic transmissions.