Lots of people can, you "just" need NCS Expert and the associated files for the specific car you're working on. These programs and files come with the diagnostic software you buy on eBay (along with INPA, Tool32, etc).
I've coded my last two cars (E36 and E46), but haven't got round to doing anything on the Z yet.
Coding isn't for the faint-hearted and I wouldn't do it for anyone else because of the risk of doing damage, but it's easy to learn and cheap to buy