Lexus IS-F only comes in standard V8 that produces about 417 Hp and 371 ft. lb of torque. Turbocharging a V8 is possible and will dramatically increase performance. Maybe the next generation may receive twin turbos because the ISF's competitors are dropping the V8s and going to V6 Turbos. As for "premium edition," I am not sure about that, I do know that there will be a CCS (Circuit Club Sport) edition for next year. This includes lots of carbon fiber body parts along with 120 lbs of weight reduction.
http://blog.roadandtrack.com/big-sho...tion-lexus-is/