You can have a someone program your vin into a ecu but it will set that ecu into what you computer was set as for what the car came with in from the factory . Someone will have to go through all the files and adjust them .
I ran into this problem when I did the swap you did . I ended up getting a friends vin number off of his 2000 Gtp and had a company program that into a ecu so that I could at least have a stock Gtp file .
You could also maybe find a 98-02 ecu from a junk yard out of a Gtp and slap that in .