depends on what sort of restriction it has. Most have a reduced exhaust outlet valve which restricts the air flow from the engine, some are missing parts such as an additional exhaust part which improves air flow which opens at higher revs. Best bet is take it to a bike garage as you may need extra parts.
I don't know but if you can catch him you caould ask the young guy on the moped who overtook me yesterday doing about 75mph.....quite how he managed it i'll never know....but he had guts to go at that speed on that type of vehicle.