i would assume below the jets, tubes and everything,
essentially the point in the inlet route where the fuel pretty much becomes the mixture that will hit the head, which of course is quite different to the throttle body which doesn't pick the fuel until passing the injector nozzle further down the route,
which could well coincide with what else i've heard, and that is that the alfa boxers suffer with low air speed until higher in the rev range, making them the revvy engine we love, but not the torquey'ist beast lower down,
so the extra length in the inlet route would, i assume, lead to better atomisation of the mixture, compensating slightly for the low air speed, so this works with a semblence of greater efficiency than the standard throttle bodies, working at low air speed and not picking up the fuel charge until very late in the route.
have i made sense?
i'm sure someone far cleverer than i can explain it better, but trust me, some extra length is reputedly a good thing!
isn't it always?