I heard about nvidia banning the gtx 660 ti Power edition triple overvoltage. Well the thing is that I bought a gtx 660 ti PE OC late on august. I know i got the old non banned card but i'm wondering if new drivers from nvidia will also lower its close performance to the 670 when overclocked.
No it would not. The card is not really overvolted out of the factory, but the potential is there. What MSI did was change voltage regulators to allow more power to the GPU core to allow for better performance at a given clockrate.
I would suggest you do not OC this card at all, keep it at stock. If you force more out of it it may burn out on you. Many of these Power edition 670 and 660ti have gone to hell, even at stock.