I've got a 2013 Polo 6r gti. It has a metallic rattling sound ONLY when accelerating around low revs. I've tried looking everywhere to locate it and can't seem to pin point it. The sound had gotten louder and louder over time. Having the car on a hoist and listening with a stethoscope is hard to pin point as theres no load on the wheels. But the sound seems to be loudest from the bottom, around the sump.
Have looked for the standard heatshields/pipes/lines but nothing causing it. have also recently had the clutch and flywheel replace so it can't be a flywheel rattle.
I've just recently dropped the sump to clean the pick up and check the oil pump and all was good. The noise had gone a bit quieter after cleaning it all. But it is still there regardless.

Has anyone experienced this ? Anything else I should check to see? Any help would be appreciated, Thanks

Video here is best I can record while driving.