CJ Ponyparts (Allentown Blvd., Harrisburg, PA)has an upgrade turbo kit for RS---the new turbo will support up to 520 hp! (IF you have all the correct other ancillary components!) I'm not so sure adding more HP is a great idea, though---just got a factory recall notice that I may need a new head gasket or new head in total. Car has 2300 miles on it, 2017, new Oct. 3rd! Early reports had RS engines "grenading" so I'm just guessing that they are near the top of their design hp(?) Interestingly, BMW got 800 hp from a 1.5 L engine in the 1970s for F1, and they also got 1200 hp from that same blown mill for qualifying---but it would ONLY hold together for those qualifying laps. Something tells me that to get that much power, the block and EVERY component must be built for it!