"Hi, I found this part today in the morning but I don't know what is it , it is just connected on exhuast pipe and when I turn on the bike it makes vacum ( like a vacum cleaner )
http://tinypic.com/view.php?pic=2ho8jrc&s=8#.VQ6POvnF8gc
http://tinypic.com/view.php?pic=1zlg2gk&s=8#.VQ6PVfnF8gc
http://i60.tinypic.com/2ho8jrc.jpg

What kind of moped is it ? From the looks of it without knowing anything about it it resembles a inline filter.

What make and year moped? Where was this actually attached? It looks like it is supposed to be bolted somewhere. A picture of the unit and where the line goes to would be useful.

Obviously unbolted from something and I believe there is a missing hose. Looks like something in an evaporator, fuel return or emission system.