128 is borderline with 192 being optimal. You should be able to put a lot more songs on a disc.
I can't seem to get any MP3 playback on my car with no iPhone, Nav or premium sound. The discs work fine in my wife's 335 with iPod. Went to the dealer to ask what the hell. They had no clue either.
Let me get this straight... You are swapping out parts designed by some of the top engineers in the world because some guys sponsored by a company told you it's "better??" But when you ask the same guy about tracking, "oh no, I have a kid now" or "I just detailed my car." or "i just got new tires."