Ecu question

Okay, here is the problem. I have a 99. Engine and trans from 02. I am buying the ecu from a 2002 that is modifiable. Reason why is that my 99 doesn't have an immobolizer. 02 does have immobizer built into the ecu. My problem is when I install the new ecu I'll be able to get Mitsubishi to flash it to my car but they can't deactivate the immobolizer. There is some minor valuable info on the forums regarding this and how to correct this problem. My friend has a system called rom raider and also ecuflash which he thinks may work. Instead of just wishing that works I'd like to try and see if someone on here can shine some good knowledge. Whatever fix is out there I need it asap. Whether it's disabling the immobolizer or some how bypassing with some aftermarket system to trick ecu. Thank you in advance!!!