Used half a tin of this each time on my last 2 fill ups, big improvement on engine noise, especially idle, always a bit dubious about these additives /cleaners but highly recommended.
not cheap, but does what it says on the tin. well worth sticking half a tin in the tank before a long journey, get that temperature up and let it do it's job.
oh and take a funnel to the pump, impossible to get it in from the tin.
[FONT=&] BG 109 Compression Restorer Engine Oil Flush same guys as vespa 166 fuel additive, its on ebay
I had recent oil change and engine flush, noticed a improvement[/FONT]