Yea they use the SOHC ka for racing making around 250hp n/a, no one uses the DOHC cam KA cause it puts you in the same class as a turbo FC.
but people have been using S13s for awhile now WAY before the drift craze, there pretty sucessfull with it also, the scca runoffs a S13 and 2 S14s won there class championship in three classes 3 years in a row.