A legit system mag will not have any PB's on it. The reason being, in order to make one you have to create a Mark 3 mag (using the Kit of Mark3 mag cell) on a mag between the levels of 5-9, which means that it would never have had the chance to evolve and gain a PB.
heh I forgot to answer your other question. The mag cells can only be obtained during the Halloween and Christmas periods. They are droppped by seasonal rappies (either a Hallow Rappy or St. Rappy) in Episode 2. Here is a link that shows the different cells that they drop
<font size=-1>[ This Message was edited by: VioletSkye on 2004-01-22 18:43 ]</font>