What are the functions in the flash that read/check the immo EEPROM and verify vin?
I'd like to code Vin into flash and check if vin in flash matches vin in EEPROM
What is your final target? Tuning Anti-copy?
IMHO than it's more easy to patch ECU warm init process with some (VIN or any another special marks) checking routine.
If OK than routine ends with "ret" command, if not OK ends with "srst"
Ecu will be virtually "bricked" (go to endless init loop) - no start, no answer etc...