Twenty years ago this month, N.W.A. were doing good. Songs like "Fuck the Police" and "Gangsta Gangsta" had traveled from the inner-city streets of Southern California to backyard barbecues in white suburban towns. While the group was on a nationwide tour, their album Straight Outta Compton sold its millionth copy. They were making it. But it took the promotional touch of the F.B.I. to really blow them up into megastars.