BMW Repair: noise when accelerating in 1st/2nd/3rd gears, intake manifold, air intake

Question
2000 328i, 100K miles, manual.
when I accelerate with the clutch completely disengaged, I hear a loud almost grinding sound.  I say grinding, but I DON'T think it is a metal on metal thing.  Instead I think it sounds more like an air intake / combustion issue.  Hard to describe.  Possibly a malfunctioning sensor causing the wrong ratio/combination of something.  I don't notice any slipping.


Answer
Hi Tim,
Try this first: on the left rear top side of the engine
(left is driver's side) is a connector to the DISA valve which is attached to the intake manifold, detach the connector while engine is running and you are hearing the noise. If the noise dissapears, then replace the DISA valve.
If this does not address the problem please let me know.
I am assuming that your clutch is functioning properly.
Regards,