Also did this. In the box it weighed 13.8KG. There's still a bit in there that I was too lazy to get. It's probably an extra 1.5-2KG. I got sick of the heat though and stopped
Next step is to remove similar amounts of weight from the front. Probably remove the A/C since it doesn't work anyway.
Small change but I really like it.
One of my transmission mounts was old and cracked. It actually felt like there was a significant amount of movement in the drivetrain because of this as it was real hard to change gears while braking.
I may have gone a little overboard, but I bought a set of Condor Speed Shop Solid UHMW Engine/Transmission mounts. They're still in transit.
Put my Momo on there too. It had a good condition M Tech 1 wheel which is now on the wifey's 323i.