If you go onto
www.ducati.com there should be all the year by year model specs.
Being a saddo anorak type person i've also got a book at home all about the 916/996/998 history published by haynes which lists all the differences and also the whole development story.
The basic 996 came out in 99 and produced 112 bhp, showa suspension.
There was also an SPS 123bhp version in 99 and 2000, with Ohlins shock, but only the 2000 model had Ohlins forks.
2001 model year there was still the standard 996, along with the 996S (similar 123 bhp engine but not quite the same to previous years SPS, i think it had SPS cams but maybe not the Ti rods, Ohlins shock, showa forks).
996R was also a 2001 model, with full Ohlins and the first 998cc testasretta (135bhp) motor that was used in the 998S year 2002 models. All 2002 models had different versions of the 'stretta motor.
Hope that helps a bit
[Edited on 9-2-2006 by BDG]
One other fact is the sports tourer ST4S actually claimed 117bhp, more than the standard 996, go figure
[Edited on 9-2-2006 by BDG]