UPDATE!
After doing the mods and installing the tune, all I can say is the change is amazing. I always viewed the Z4M as a sort of "Dr, Jekyll and Mr. Hyde" type of car. It can be civilized when required, but will turn into a beast when necessary. The tune along with the headers and VT engine mounts have made this analogy even more relevant.
Now, it is still very subdued when I am driving like a responsible person. It does feel like the power curve has moved up the rpm band ever so slightly, making it even easier to drive like an old man IMO. Unfortunately it has rained nearly every day here so I never got a chance to really give it a stretch after the install, but when I did get a chance to give it the beans, just...
It feels properly good, and is even better to drive in a spirited fashion now! Even more exciting with sport on and traction off. Definitely happy with the tune, thanks everyone for your help!