By most accounts, there were about 400 shipped to the US for one model year only. Some accounts say that there were only 250. They were followed with the SS series in 91.
The best place on the web for the 1990 Nuovo Sport is ducatipaso.org There is a separate category for them there, and lots of similar souls, as the Sport borrowed lot of parts from the Paso. Lively discussions about 16" wheels, Weber carbs, odd clutch parts, and more.