For GM cars, there are at least two companies who offer software capable of reprogramming the computer controlling the fuel injection system. This includes all look-up tables and turning off and on the control "flags".

Are there any companies offering software with this capability or users groups doing this.
from what I understand the BMW file sizes are much smaller and efficient than the GM equivalents (especially the early Motronic 1.1 which only have a 2k memory prom holding the program and tables) so the decompiling wouldn't be much of task.

I'm a mechanical type and software isn't my cup of tea.