No it is ot the tie-bar - had the engine out and replaced the DMF (DMC) and checked all the gears in the chain from crank to pump, replaced water pump (gear driven) and re-furbed all the injectors (engine actually runs very well now) apart from the rattle which comes from the HP fuel pump - you can detect the source easily using an engine stethascope readily available in the car shops for few quid.
Noise is probably the pump labouring to pump max fuel at max pressure at idle and this is overloading the pre-load spring on the dual pinion which drives it. At increased revs the noise disappears as the pump can now copes OK.
Also engine rattles the belts if you take off from idle speed due to the injectors having 1600 bar instead of 300 bar for a quiet idle and smooth take-off. Also get excessive carbon on the EGR
(Need to clean it every three months), in the exhaust build-up, and when aceelerating, which all point to over-injection and poor burn due to rail pressure bieing too high - in the end there is a safetly bleed-off at 1600 bar if the regulation fails and this is where mine car sits all the time probably. Normal range is 300 bar at idle to 1300 bar with pedal to the metal.
Got the idea from similar problems reported on the Volvo site.