When you bring up the new instance, attach the PIAF disk at device /dev/xvdb or /dev/sdb (I forget but the EC2 console will make it clear). Then when you boot up your new temporary instance, log in to it over SSH. Become root and issue
Then your PIAF disk is available at /mnt. Now cd to /mnt/etc and look in the rc#.d directories for files matching "S##iptables". Those are the symlinks that tell the OS to start (the "S") the service, and the number is the order in which it starts. Remove those S##iptables symlinks so that iptables won't start at boot. I believe CentOS starts at runlevel 3 normally, so you definitely want to clear the S##iptables out of rc3.d but might as well remove them from the other runlevels too.
You could also edit the /mnt/etc/sysconfig/iptables file to let yourself in. I'd recommend just turning off iptables on EC2 and using the Security Groups firewall system. You'll likely get differing opinions on this.
When done editing the PIAF disk, cd / and umount /mnt and then shutdown the temp instance, put the volume back on the PIAF instance, boot up, and see how it goes!
Code:
mount /dev/sdb /mnt
You could also edit the /mnt/etc/sysconfig/iptables file to let yourself in. I'd recommend just turning off iptables on EC2 and using the Security Groups firewall system. You'll likely get differing opinions on this.
When done editing the PIAF disk, cd / and umount /mnt and then shutdown the temp instance, put the volume back on the PIAF instance, boot up, and see how it goes!