FOI is used in vanilla d2 PVP for the extra 20ias on GMB bow, allowing you to use a rare 2zon/ 30frw/2os / 3 other stats helm to reach max IAS Break point while using Fort and 2x 15ias jewels in helm.

If you use regular Faith GMB, you have to use a 3os Magic helm with 3x 15ias jewels.