The BCM processes the info for peripheral systems and accessories that do not have a direct affect on engine / drivetrain operation. Every aspect of this car is monitored / manipulated by one module or another... ECU FMU (engine & fuel) PCM (drivetrain) BCM (body parts & accessories).

With regards to the original post... The real engine management is handled by a small EPROM chip that is soldered onto the mother board. This contains the operating software... Removing the original EPROM from the motherboard is what takes place when you send the ECU to a "tuner" to get it flashed... The reason it must be removed is because it circumvents the OEM security measures that are built-in to prevent manipulation of the software... It's a tedious task that should not be attempted unless you have experience removing them from mother boards... That being said, instead of purchasing a new ECU (mother board) I can get you a new EPROM chip and install an "old school" clip device that allows you to pop the chip in-and-out with a pair of needle nose pliers... Then we can copy your OEM software onto the second EPROM and you can mess with the maps with the security of knowing you have the OEM operating system backed-up.