This might sound stupid but is it possible to cap 1 of the outlet pipes at the end of the down pipes and run 1 end can? Seems so easy but what effect would it have on the engine if any? I take it that it would be louder.
Would be interesting to know. If you know a reason not to do it let me know. Could turn out to be a cheap mod.
The gas flow will be all to rock, probably too much back pressure and the proformance will suffer. You would definatley have to rejet and Vespas would beat you off the traffic lights with ease 
