John W
The 998s does indeed have the 2001 996R engine which is a deep sump testasreta lump, However I believe it does not have the `R`s` Ti rods.
It has different cams to the plain 998 and a larger bore exhaust system.
Not sure about a different engine management system but as I have replaced mt exhaust with a Termi system, it comes with a new management system. By changing the exhaust and "chip" to a Termi system a 998s puts out about 130-134 at the rear wheel, I have also fitted the JHP undertank filter system which definitly makes the engine "crisper".
All in all the s model is a better bet to go for if your in the market for one. For your own interst there were only 27 998s monoposto`s imported to the Uk of which only 7 were in Yellow, for you Essex chaps that means that 20 were red!
