Is it possible to flash the stock file of a 180hp Golf/Jetta/Octavia to my AUM (k03s VVT) 150hp Octavia? As far as I know these engines are identical, the only thing that changes is the factory map, the 180hp cars have more boost. Can I download a oem 180hp map and simply flash it on my car with a vagcom cable and nefmoto?

Maybe it is possible, but not recomended. It can mess with your immo.

You can of course, so long as the bootrom is the same in each file.

There will be a ton of differences though which may give you bad results... Better to have a look at a 180bhp file and compare/make the changes yourself to your own file