08 B6 2.0 TDI shaking under acceleration

[Mekon88]

Hi Folks,

Picked up a 2008 B6 Estate yesterday, it was advertised as spares repair with a fault if you boot it over 3k revs which I figured I can diagnose at leisure as I mostly keep a diesel below 2k revs on my back road pottering about however the car has a fault I was not aware of (and was not described in the advert) until I got a little ways up the road, it shakes alot when trying to accelerate.

Vibration does not appear to be linked to engine speed directly as gently taking it up to 3.5k (using like 10% throttle on a flat road) doesn't induce shaking.
I was able to gently get up to motorway speeds so I don't think it is transmission, wheel balance type issues as speed doesn't appear to be the factor.
No error codes on dash
No codes coming up on my cheapo bluetooth OBD tool (stop laughing it does OCCASIONALLY prove useful)
Vibration CAN be induced by using approx 25% or more throttle even in low gears (e.g. pulling away at junctions) but will immediate cease if I back off the throttle.
According to el cheapo OBD boost pressure appears to be as I would expect.
It feels lovely and smooth at idle, when up to speed and at low throttle positions but under acceleration it feels like its dropping 2 cylinders

I have a couple thoughts in mind, given that to my untrained mind the above would appear to indicate a fueling issue, do we think that chucking a new fuel filter is a good first stop (based on the notion that as a service item it cant really hurt and is cheap)
Or do we think maybe injector loom? could that be okay at low output and then losing an injector or two at stronger throttle positions?

Any thoughts welcome and diagnostic ideas are very welcome