Mark, first of all thank you for trying to solve this issue for us.
Finally I got my new car and had my empeg+radio installed. So I could test it today. I DISABLED the AF function from the hijack menu, but unfortunately, it still changes stations; anyway I had the impressions that few times the radio tried to resync to a different station but then remained on the one I was listening. Probably there's more to filter out?
I still see "RDS" on the display, so I guess not all the rds data is being blocked.

Please, let me know if there's any other info I can give you, no need to say I'll be mor ethan happy to do so

And by the way, it is great to read you all. Very nice to be back from vacation!