The obvious restrictions are in the variator and the exhaust system, which are easily changed or removed, here is a link to show you what should be removed from the transmission on a 2 stroke engine which is exactly the same principle for your 4 stroke, follow step 4 and 5 .
The exhaust system also needs liberating but don't expect an increase like you would receive on a 2 stroke which in some cases could be double the top speed. A good system which is stealthy in it's appearance is the Tecnigas Silent Pro . This offers low noise, improved top speed and freedom for the engine to rid itself of the gases.
The CDI is key to achieving more top speed, previously the only way to get past the electrical restriction was to cut part of the circuit on the CDI and re seal the unit. Now you can unplug the old unit without visiting a Piaggio specialist and plug the new one in it's place, the offer price is only £31.00. Although only an approximate figure we would expect you would see between 45 to 55mph with the components mentioned.