The operating system for ECMs changes nearly every year for the C5s. The '97 and '98 in particular have quite different OS and even wiring harness differences vs the rest of the C5s. You will have to have someone flash a '97 Operating System to your new ECM in order for it to work on your car. It will take something like HP Tuner or EFI Live to do that. I know with HP Tuner it requires a license for the ECM and a license for the tune you upgrade it to. Get back in touch with SSP and see what they provide to you.