Every E85/E86 Z4 uses the same 6-speed transmission (the 2.5i had a 5-speed though). Many of your points have more to do with wear/age and general changes that were done for the 2006 facelift or as production evolved.
And you didn't even mention the limited slip diff.
You could try something like this for a simple bluetooth solution. Just plug it into the AUX input.