Mine isn't a 20 but I've posted several times about it. mine has been in the shop several times already for this issue. Ford told the dealer that they couldn't do any service on the turbos, they had to do the phaser repair first. So after a week in the shop for that, still had the rattle, the second time around they attempted to replace the wastegate actuators, and that still didn't fix it. so now I'm waiting for an appointment to go hopefully get the turbos replaced. My noise is happening on both driver and passenger side. not only does it happen when you start the vehicle, but it can happen after 10 hours of driving. Pretty annoying.
But as an FYI, Ford actually distributed a dealer service bulletin to all of their dealers, stating that rattles like this are normal and that under normal circumstances they won't hurt anything, therefore they don't tend to fix them. many people have different experiences at their local dealers but my guess is it'll get harder and harder to get this thing fixed.
It still kills me that an $80k msrp vehicle sounds like a geo metro in a drive thru.