1998 323is with stock changer.
I burn audio cd's at 48x (cd's max speed, burner can do 52) and that's all the changer ever sees. I have used about 6 different brands in the player with zero problems. You CANNOT burn mp3's onto the cd in data mode, you must burn the cd as a standard audio cd (which decompresses the mp3) and you can only fit 80 minutes of audio onto it.
Most new aftermarket cd changers can play MP3's in data mode, (you can store a upwards of 5+ hours of music on cd's that way) but to use those you usually need an aftermarket head unit, and if you do that, you might as well replace the stock amp in the back or bypass it (IGCH!)
Pirate Nero Burning rom and burn audio cd's that way, I love that program. It's got an easy mode, and an advanced moe where you can change just about anything.