W201 190E Fuel Pump Noise

[Synched]

My 1990 190E has only 32000 km's now, when I bought it in '08 it had less than 15k, so it's like new. Though one thing is a concern...the loudness of what I think is the fuel pump. It's almost a constant loud hum, coming from the rear right hand side and can be quite aggravating. I don't recall this being the case before, seems to have begun soon after a local mechanic changed the fuel filter...not a MB mechanic mind you, as there are none where I live in Argentina, so I wonder if an OEM filter could be the blame?
Any ideas welcome as I am not mechanically minded ! THANKS !