Air intake adjuster

[Impulse]

Dear members,What does the adjuster do? You know, the little rectangular blackbox right behind the dipstick of my 325i engine. It is mounted next to the intake manifold which suppose to contain a valve operated by a diaphragm and with only a wire attached to it.My mechanic from one of the UDM shops said ,failure of this gizmo will not be pick up by the ECU .You can see whether it work when you start and crank your engine,the little arm linkage start to move in and out.He told me to change it b'cos this will effect the operation of the 4,O2 sensors and might get damaged in the long run.(O2 sensor cost RM$500 each) and I change the adjuster to the tune of RM$920!!! ,thinking that I save on replacing the O2 sensors.I really don't feel any changes on my engine after and remain the same as before.Am I been short change???? or just wasting my hard earned money???More stories to share later.BTW, I am driving an E46 325i 2002 model.Any info is welcome.Regards,Impulse