I hate to bust your bubble but the only thing a scooter uses less of is gas, emissions are MUCH higher than modern cars....
B&L - good stuff, and link. I always assumed this was the case. My GV250 - all stock, smells NASTY!!!!! when the exhause catches up with me at a red light. Gross polluters! But at least the mpg is good and not many on the road.
Yesterday, I saw a brand new (6 month ago mfg date on the sticker) Yamaha FZ-09 3 cylinder motorcycle with stock exhaust which already had black carbon soot on the tip of the exhaust pipe.