This is the easier method to improve the turn signals luminocity on Piaggio MP3 250-400-500/2009. No resistors, no new led signals, no contacts modification. The only needed is the new Piaggio relay 1D002536R and four led bulbs BAU15S (Amber, 360degrees).
To avoid the Hyperflashing phenomenon, it is necessary to change the old analog flasher (which all MP3 have until 2018), with the new Piaggio flasher relay 1D002536R. (Price in Greece = 26€)
Many thanks to pinheadh78 for the informations about the relay.