What's the Audi part number then?
Every Audi forum I've visited over the last 10+ years has had posts from Audi owners saying:
- Symphony II internal CD changer plays only audio CDs
- Symphony II+ internal CD changer plays audio and MP3 CDs
- glovebox changer only plays audio CDs not MP3 CDs, regardless of the head unit (as already said the Cd changer to head unit connection is analgoue)
And you're saying different to that...
Are you 100% sure the tracks are saved as MP3 files and that your burner hasn't changed them to audio format (as that's what Windows Media Player does when you tell it to burn a CD from MP3 files)?
Try taking one of your "MP3" CDs out of the glovebox changer and putting in your PC - what files are shown? It wouldn't surprise me if they are not xxx.MP3 but xxx.CDA files...