That is EXACTLY what I'm trying to tell you!
Look, Joe, they start to '4-stroke' at about 27mph, and the top speed is 29mph. Note that they go exactly under 30mph, so they would meet the requirements of the LAW. They aren't flooding the motor, running an entire jet size too rich, or fouling out plugs, or hindering it's ability to run in any way what.so.ever! They'll run for thousands of miles without modification. But as soon I open up the NOS air boxes and NOS air filters, they gain a couple mph, as well as stop 4-stroking, and the resonance of the pipe no longer exists, which is exactly what Craig was describing. TRUST ME, Joe.
They were restricted from the factory. All mopeds were, in too many different ways to count!
Some old Sachs in Germany have an IDENTICAL motor; the exact same 47cc top end and exact same crankcase, stroke, etc., yet they were restricted to go only 25Kmh (thats about 18mph!). They have a smaller carb, even more restrictive air filter, smaller jets, and a tiny header, to make them _just slow enough_ to meet the speed restrictions in the Law.