Don't ask how I found it, but I read an old thread on this subject from years past. Most of the talk was favorable, others ,beh. But I think their Vespas were stock. Mine is a little upgrade, 13:13 carb/ # 69 jet hi flow air filter, polini circuit pipe. I hope to get 35 -40 mph , just so I can get away from irritated drivers who don't think I have a right to ride. So no pain no gain! It's about 40* out going to do it.