Hey Anna,
My outbox on my SAU account is full so I'll just reply in this thread for you.
The cam valve will be the thing causing the seat to squeaking when you lean to the left.
If you have the same issue when leaning to the right as well then it will be something much more sinister.
Try get a few pics of your engine bay around near your turbo and I will circle the spot you need to adjust.
Cheers,
DK