The major scooter brands are putting cat converters on their 2 stroke models (the few they sell)
http://en.wikipedia.org/wiki/Yamaha_Zuma

The 4 strokes have them as well, from the major builders, I have no idea what those cheap chinese scooters have. All I am saying, and I will not get into this argument as I have done it to death on jetski boards. 2 strokes can be (not all are) more efficient, and cleaner running, and certainly more powerful than a similar displacement 4 stroke. If anyone is interested they can certainly look it up, the technology is out there, however, it is not widely used because the majority of the population relate the 2 stroke to the noisy nasty engines of the 70's and 80's or weed eaters. It is too bad, the MPG a 2 stroke can get is amazing, maintenance is a SNAP.