I saw you posted this question to the ACF author too, which is really a better place to start.
Unfortunately, I didn’t see any answer about how to generate the extra underscore fields that ACF seems to need. Requiring someone to be sitting at the screen to create those fields seems to pretty much rule out any kind of import, doesn’t it?
In any case, if you can get a function or PHP code to generate the fields you need for ACF, I’ll be happy to add a filter to TurboCSV so you can call it.
Also, I have two questions:
1. What happens if in the WP admin you go to the list of posts, select a few posts that are missing the ACF fields, choose ‘bulk actions’, then ‘edit’ and then publish the posts? Do you get the missing hidden fields then or are they still missing?
2. What kind of fields are you importing? Are you using ‘advanced’ functionality or just ‘regular’ data (like text or numbers)? Or does ACF require those special fields even when the field contains regular data?