What race cars have power steering, and which ones don't?

i was having a conversation with one of my clmates about the use of powersteering on race cars today. I think that the gyroscopic effect of car wheels would make it an absolute nessestiy at the speeds seen in ChampCar, Indy, Nascar, ect. but on the other hand they would add weight and one more element to go wrong?-experts? (Nascar, Champ, Indy, LeMans, anything larger than a shifterkart)-thanks