I think there are many more differences than the obvious and the brochures. Even studying part numbers does not work, as Outrun mention, parts bins were raided, and things were tweaked. The "diamond polished internals" was actually a full balance and blueprinting done, engine by engine, on the early models (that's what my MD told me, the service manager saw one being assembled in the factory - although I may have missed something in the translation).
The software is also tweaked: brakes, gearbox, engine.
Regarding the weight: again a conservative estimate. The bonnet is alloy, very little sound deadening in the whole car, no rear seats, bucket front seats with no electrics (two seater).
Just driving in Race mode one can feel how nervous the car becomes, higher shift points, lumpier idle. Also, find a stradale that under-performs on its brochure figueres: you won't. They all seem to over-perform. For sure these were little play things that someone in the Maserati factory was very happy to build, not quite letting on to big brother what was going on. I'll put mine on the dyno one day just to shut myself up!