hi guys, i'm from italy, sorry for my bad english. i also have a 125 dt re 2006. i think something similar happened to me about 2 months ago, it was sounding and running like as the "magic wire" wasn't connected, i tried to disconnect and reconnect it but nothing changed. in the following weeks i canged the piston rings and now is as fast as before! i didn't changed also the piston because it was in really good conditions. i hope to help