Yes, they do use the SXS parts right from the factory. They keep a watchfull eye over these parts and they are quite "tight lipped" regarding the specs.
You can get the Doma pipes right through KTM Hard Equipment 2001 #SXS.00.125.501 and #SXS.00.125.551. The motors use different cranks, pistons cylinders, heads, carbs and transmissions. (whats left?) I believe the electronics are also changed.
Thanks for all the info. I'm just trying to make a fast bike for an intermediate(my little brother).If you do know what they use that the normal man can get.