Hi,
Mine has literally just started making a similar noise this morning.
I'm new to my 8l S3 and so far so good, I last checked the oil on saturday and it was half full. After some hard driving yesterday in the blistering heat, I drove home, let the car cool down for a minute or two before turning it off and leaving it over night.
This morning I was a little late for work so I could only let the car warm up for a minute or two. Once the car was idling almost normally I left for the office and didn't start to drive it harder until the temp was around 90. I might have hit a pot-hole but then it wasn't a large nor deep one... shortly after the "oil level low" warning came up on the dash and I didn't take it into boost from then on. However, it sounded alot like a diesel and I drove it for another 3 minutes until coming to a stop at my office. I didn't check the oil and topped it up (a little too much as I've just found). The oil level low warning has now gone but has been replaced by the engine management light being solidly lit.
With the 5vTurbo cover off the engine I think I can hear the noise coming from the right hand side of the engine block (facing it). I'm sure the noise only appears whilst the revs are climbing and only at 2k rpm. From what I understand the car is unmodified but may have been remapped by the previous owner.
Any advice welcome, I'm not great with cars! If you need further information please do let me know.