These are likely just a subset of ECU firmwares used during each model year. If you have an ECU with a different part number and firmware on the case, share that info with us or update the list. Superficially, the 96 and 97 firmwares are very similar, and the 98 and 99 firmwares are very similar. Some of the offsets are the same, the base code they were compiled from is likely the same.