about the question how to recognize an aftermarket carb job. Usually that`s easy. If you go down in front of the bike and look below the fairing you will see the carb and above it the black airbox.
Usually aftermarket carbs don`t use any airboxes because they don`t fit and making a new one is usually too much work for most, so the put on aftermarket pod filters.
The original carb is positioned on a short 2in1 inlet manifold and the carb is a big, bulky car type one.
Del`ortos are single carbs which sit on a short single inlet manifold. Usually they`re used with open foilters too and one filters shows to the front the one of the standing cylinder to the rear.
Mikunis, the carbs used on all other newer carbed Pasos have long single inlet manifolds and the carb itself is basically 2 carbs placed side by side.
This just to give you a rough indication.
otherwise see here the Mikuni carb:
http://forums.ducatipaso.org/viewtopic.php?name= ... cle&sid=29
and the Weber:
http://forums.ducatipaso.org/viewtopic.php?set_a ... _photo.php
Gerhard