Just got a 2007 S4 Cabriolet with navigation. Since it doesn't have an ipod adapter I tried loading music onto a 2 gb sd card. I put about 80 songs on from itunes and converted them all on my mac into mp3 format by resaving them as a .mp3 instead of .m4a or .m4p. When I put the card in, the list of songs shows up on the screen but only about 5 of the songs will actually play. I believe these few songs that play were already in the .mp3 format so i did not edit the file type to convert them. Is there something I need to do to convert my other songs from itunes to the .mp3 format instead of just resaving them with the .mp3 extension?