George,
That upgrade file, is in fact an upgrade file for your PS-3 engine. Most likely the chain file has an update. May fix some glitch in the original file.
Please clarify something for me.
Upon downloading and inspecting the two sets of files, it appears that the Chain files are identical. This is based on determining that both files have the exact same name, are the exact same length in bytes and have the same creation date.
The sound files, however, appear to be different. They have different names, sizes in bytes and different creation dates.
The above would lead me to believe that the upgrade files are for upgrading non-DCS engines to PS2 (3 volt board) or PS3, while the production files may be newer copies of what came with the engine when it was manufactured.
Would I be correct that Chain files In both cases would be for the diesel PS3 board, since it is what's both in the engine and in the diesel upgrade kit?
Also, it wouldn't make sense to me to have an older, replaced sound file available alongside the newer sound file that replaced it. Instead, it would seem to make more sense to have the latest production sound file and also an upgrade sound file available.