My 1998 has a 2005 or 2006 single CD player in the dash, it plays MP3 CDs but I don't have the extended magazine changer ... in theory it's just a CD laser that's reading data and the head unit does the processing... technically it could work.
I'll see if I can find someone with a changer and plug it up to my HU and see if it does work. If so it would totally be worth upgrading the HU in your car, I've seen them for $300-something on eBay.. which is where mine came from according to the PO. He didn't know it played MP3 CDs tho, he said if he had known that he'd have kept it!
