you are right about the jet, you can open up the holes in the restrictor dish in the air box, but you might want to get a handfull of jets up into the mid-50s range. Other thing is the polini long country will give it a bit of power and a few mph at the top end, but it kills the low end so it kind of sucks with the one speed, works ok with a variator so I would suggest that (variator and rear transmission from variated vespa), or a tecno estoril which is a good low-end pipe.