the standard exhaust is in 2 parts , the first part and I think the last part too has a restrictor , also the variator is resticted by a ring , and fully unrestricted the main Jet should be 72 , then the scooter will perfom on it's max. to go a little bit faster you can buy a racing type exhaust on it like Gianelli nrx (specialy for area) , leovince sprinter , and some other exhausts , most exhaust for a normal minarelli motor do not fit this bike. the main jet should be 76/78 with a racing type exhaust with a std airfilter. 92 like the user above said is withhout the pipe in the airfilter , but removing this pipe had no use at all!!
I have a Aprilia Area 51 myself , there are not many exhaust that wil fit!