C5 X7 - low speed 'snatching'

[steveclv]

I'm still getting used to my 'new to me' 2009 C5 X7 auto tourer (155k miles)

When driving at low town speeds as you feather the throttle, I feel that there is something worn somewhere as the car 'snatches' between on and off very light throttle - it's hard to describe but does make low speed driving a bit unpleasant - it's typically in D3 but doesn't seem to be gearbox related - more like final drive and if it was RWD then I'd suggest a universal joint.
There are no noticeable clunks although at speed there is a kind of weird howl faintly in the background - I don't think it's wheel bearings as they tend to grumble.
Can anyone think of what I need to be checking?

[Estately]

Could this be caused by air getting into the fuel, say between the filter and injector pump, if this is a diesel.

[steveclv]

I'm almost certain it's not engine related but drivetrain. If it were air getting in then I'm sure there would be other symptoms and engine wise she is sweet and giving me 45mpg average. I'll have to try and get some diagrams of how the drivetrain is built up - maybe it's CV joint or driveshaft related. I did wonder whether the butterfly valve needed a clean given that it's just at that very fine on/off throttle position at low speeds but when I looked at where it's located, it's not like my petrol cars where they gummed up - it's located a long way away from the combustion chambers.

[furriegurrie]

I’d check your engine mounts for excessive movement

[Stickyfinger]

and lower suspension mount/frip joint (you need a leaver to see movement as the suspension is in compression)

[steveclv]

Thanks - I am beginning to suspect engine mounts. Can someone explain where they are located (apart from the top one which is obvious LOL) and are they DIYable without special tools? Thanks