"Witness to the Mob" IS about Sammy Gravano. It isn't a very good movie, but its worth the rental fee just to see some of the alumni of mob actors in its cast - Abe Vigoda (Tessio) plays Paul Castellano, and Richard Bright (Al Neri) has a role. From "The Sopranos" comes Michael Imperioli, Vincent Pastore and Kathrine Narducci, and even Frank Vincent (Billy Batts in "Goodfellas") is in it.