Since 9.0 upgrade my iPhone and Edge 820 will no longer remember the paring, plus route calculations are taking like 5 minutes, it is a terrible upgrade, I was happy with 8.80, after some digging around I discovered the file on my computer in the folder
It is likely it will be in a different folder, so just search for a file called GUPDATE.GCD, then copy this file to the Garmin folder on your Edge 820, restart the Edge and it will ask you if you want to downgrade, the only problem is you have to reconfigure the Edge from scratch again including setting up all the screens, but at least it works, if you can't find the GCD file let me know and I can send it via dropbox of the likes, I have now saved this file for future use !
