I shut off mine to get rid of that awful sound at idle.... Contrary to what I expected, the engine is a bit quieter over the whole rpm/load range now...
As I did expect, I noticed absolutely no difference in performance, but for making the scoot sound less cheap and annoying, I think it's worth the effort...
The only downside is an invisible one : the system is meant to deliver oxygen to burn some of the gasoline residues and carbon monoxide which are present in the exhaust gases...
So in theory the engine pollutes more now..
In practice these systems are not so efficient, especially in the primitive way they're implemented on our scoots...
And, in a world where large jet airliners spill hundreds of litres of unburnt fuel at takeoff, and solvent-based paint and aerosols are used in extremely large quantities, I really can't feel guilty about adding a teensy tiny bit of gasoline to that cloud...