Throttle Actuator question
 

My '98 ML320 has an annoying buzzing noise that I believe is also interfering with the radio. I've tracked the noise to the throttle actuator. When the key is position 2 the buzzing starts and doesn't stop until the engine is turned off. Anyone heard of this or can at least confirm that this actuator could indeed be making this noise. Any advise on wether or not it should be changed, how to change it, or if this should be a dealer only item. TIA.