Was your unit the cd version or the DVD version???Hi,
I fitted a MFD2 yesterday, I had a RCD300 with the factory fit changer, and it just worked, I didn't need a new cable or anything. I don't have any extra audio options either.
On another slightly different note, I followed Foxy's execellent instructions, and in them he mentions that you have to hack at the aeriel plug, I found that I didn't have to do this, I just plugged it into the MFD2.
Hope that helps, David