Hi Deli guys

I have an unusual one for everybody, my engine this past week has a funny kind of Buzz sound, yeah yeah no i have not inherited a bee hive LOL but just a funny kind of buzzy or buzz sound going on, drives ok but just a slightly rough idle compared to its usual nice smooth idle, done the usual checking of everything that i can think off, so what does everybody think i should be checking.
Oh and its an. L300
Cheers. Mario