Too much disinformation in this thread.
You cannot inject powersaves backups from other cartridges. -- save crypto is unique per cartridge
You cannot inject a save file into any decrypted powersaves file. -- save files have "signature" which depends on the unique cart crypto
You can only inject a non-edited backup from the SAME cartridge. -- backups can be restored as they are an unedited backup
You can decrypt the save using the xorpad trick (linked on previous page). -- obtain a "main" file for viewing in PKHeX.