There was a thread recently which gave the differences between the models...
I cant remeber the title of it but i am sure someone will know...
Any way i have just upgraded my 916bip to an SP3... the difference is unreal.
I was in a situation where I was unable to afford much so basically all i had was the money from the bp, plus a little that i had saved, So i suppose what i am trying to say is...
What is your budget... If money is no object then get a 998R.
The SP3 is an early model that ran until 1997.... I believe.
It has 131bhp, and i am told is a little more racey than the current SPS models of today. These beasts rev to 11500rpm, have titanium con rods,race cams, plus many other bits and pieces,
You can pick them up from 4k to 7k depending on condition......But as with any duc, but especially the sp /s models make sure them belts get changed