I have the same computer system as yours and my MINT 13 wifi now works like lightning. (Even dialup works really fast now, as far as dialup goes.) My computer is outfitted with iwlwifi, not iwlagn. (To check what you have, use terminal command, "lsmod." )
So, here is the wifi script which worked for me. In terminal:
modprobe iwlwifi bt_coex_active=0
To make this script permanent, in terminal:
sudo pluma /etc/modprobe.d/iwlwifi.conf
Then add line:
options iwlwifi bt_coex_active=0
Save changes. Can't remember if I needed to reboot.
Here is another article, which is long and technical, and shows the process of how one team solved this issue; I found interesting:http://bugzilla.intellinuxwireless.org/ ... gi?id=2325
Good luck w/ getting up to speed.