Power foci are the most potent and treasured of all. Possession of a power focus feeds a magician’s Magic directly, making her efforts more powerful in all forms of magical ability. A power focus adds its Force to all tests in which the magician’s Magic is included. A single power focus can increase a magician’s ability to cast spells, call on and control spirits, and bypass astral barriers. A power focus does not help in Counterspelling a hostile spell as it is cast, nor can it duplicate the unique ability of a weapon focus.
Power foci live up to their name. They are very powerful foci that temporarily increase your effective Magic rating. That means they add to your Sorcery, Conjuring, and Enchanting dice pools, along with any other test where Magic is involved. Power foci can take any form, but for some reason, rings and amulets are quite popular.
No significant change, all it does is state the same in other words.