If you have problems downloading packages, you can try to select the mirrors Cnchi will use by yourself.
You can use Cnchi’s new mirror page to sort the mirrors yourself, or do it manually this way:
Run the livecd
Update the mirrorlists:
sudo pacman -S pacman-mirrorlist antergos-mirrorlist
As you already had a mirrorlist, you must copy the new ones to the old ones:
sudo cp /etc/pacman.d/mirrorlist.pacnew /etc/pacman.d/mirrorlist
sudo cp /etc/pacman.d/antergos-mirrorlist.pacnew /etc/pacman.d/antergos-mirrorlist
You can run reflector to make it sort your Arch mirrors for you (based on speed):
sudo reflector -l 30 -f 15 --save /etc/pacman.d/mirrorlist
Edit the two mirror files, and leave just the mirrors you want to use (put a starting # in those that you don’t).
pacman -Syyto check that the mirrors are working
(NB: Do not do this in an installed system, in an installed system always run
Run Cnchi again but tell it to not rank your mirrors automatically, so in mirrors page select “Leave the mirrors lists as they are (by default)”, or even “Let me manage the mirrors lists (advanced)”.