Still for sale?
I had my hopes set on a 3.23 to swap for the 2.93 in my 330i for 10% more TQ. So far I haven't found a reasonable price on a 3.23. The math would seem to indicate that your 3.15 would give me 7.5% more TQ, which might be fine.
If yours is still for sale I might be interested. How much?