You can't disable the Bluetooth MP3 playback without disabling the phone connectivity. However, you can stop Sync from automatically playing via bluetooth if you first plug in your iPhone (or iPod, USB drive, etc) into the USB port (if equipped) for Sync. By default, Sync will connect to whatever it detects as connected to it, i.e. the USB port, line port or Bluetooth. As for the playback dropping out while playing in Bluetooth mode, Sync suggests that you turn off wi-fi as they claim that could be a source of interference (do not turn to "airplane mode" or you will lose Sync phone capability!). I however have had no luck with that (Sync says more iPhone functions you turn off, you allow less interference). Also beware of updating your Sync to v2.1 as older iPods (like classic) will stop working and the iPhone will constantly "index" this as Sync says is a "known problem that Sync and Apple are aware of". I haven't tried the fix yet, but supposedly changing the Apple iPod firmware to a Sync approved version will solve the iPod classic problem. You can view approved lists on the syncmyride.com website. There is also another issue with Sync v2.1 - I was told by my Ford dealer that Ford issued a bulletin that there is a possibility some model cars/Sync modules have an issue where the car's battery will drain. I know this because I am having battery problems on a car less than a year old - if you ask me, less technology in cars is a BETTER thing for all.