Hey, I tried using that Porygon-z with specs in Battle Tower Wi-fi; I swept 3 people in a row without needing to switch! That thing is a freaking monster; I've OHKO'd a steelix with specs ice beam. I must say, that thing definitely shouldn't be BL!
Hey man, that porygon did me quite a bit actually; I play UU so I turned it into Porygon2, taught it agility and after I get the agility off, its practically Porygon-Z, just able to survive a hit or two. In my recent battles I've realized that its better off being a Porygon-Z in OU, so its got the right EV's (Max Speed and Sp.A, 4hp) for that too. Can't say thanks enough!