I contacted Motorola after my Droid4 stopped working with Sync in regards to audio streaming and texting.
After months of back and forth with Motorola support, they replaced my Droid4. When Google purchased Motorola, they rolled out the 4.1.2 update to the Droid4 (and many other models) using the Google Bluetooth stack, replacing the Motorola Bluetooth stack.
This was an oversight by Motorola and they are replacing the phones on which they broke/disabled the Bluetooth MAP profile on the phones with the OS update. However, they are only replacing the phone if you place a support call to them and 'make it' all the way to their level 3 support technicians.
I now have a Motorola Droid Razr M that does support the Bluetooth MAP profile, needed for this texting functionality. I can now, once again, use this functionality.
Our car's aren't out of date, but, some phones don't support this functionality, and Motorola/Google broke many phones with upgrades.
Hope that helps....
Mark