its a funny thing to argue cause there is no definate answer, but if an rst has a zetec turbo fitted it would be sold as a rst with zetec turbo, however if a popular plus was fitted with a rst lump would that make it an rst if the engine was the thing that makes them an rst????????. Ipersonally went for a zvh because of the extra power and standard looks, i dont think my series 1 would look right with a zetec turbo imo