A little birdie just told us about stock firmware:
Vibra is not built into all units, but if yours has a vibra motor you can turn it on by issuing:
echo ro.board.has_vibrator=yes >> /data/local.prop
If you want to damage your hearing, this one is for you:
echo ro.audio.no_adjust=yes >> /data/local.prop
We’ll not be held responsible for whatever you do with this information. For all we know the unit might try to bite you or eat your homework!