I've wondered about the "DE" nomenclature, it seemed very Nissan (although Subaru and Nissan did and to an extent still do share many parts, same with Toyota). I've only heard the "DE" referencing JDM-only engines. I'm assuming it went off the fender tag that says engine family. All my USDM ones are listed as an "EJ25DA..." So I assumed the letters that followed would be changes.
