Engine shudder at 1500 to 2800 revs B6 Passat

[Scottys248]

Hi guys,
I'm having trouble with my B6 2006 Passat after an engine repair which was necessitated by the oil pump drive shaft failing.
Had oil pump drive shaft, engine block, camshafts shells, timing belt, boost sensor replaced - (engine block from another engine).

I've just had injector no.4 and wiring loom replaced (due violent shudder and very poor power after engine rebuilt) and do not want to fork out for another one if this in not the most likely cause of the shudder - All 4 Injectors previously replaced by VW in 2011.
Between 1500 and 2800 revs there is an uncomfortable shudder of the engine which is worse under harder acceleration and in higher gears.
Below is the fuel injector assessment and the auto-electrician and mechanic reckon that injector no.3 is likely to be the cause.

Injector quantity deviation
1. -0.45mg/str
2. 0.0
3. 1.52
4. - 1.06

Is it likely that changing no. 3 will solve the issue? I've been told that although no. 4 was replaced, the deviation of this is so high due to possibly compensating for no.3?

Thanks in advance,

 

[Dimitri16V]

That high of deviation could be multiple things

Were the injectors correctly installed ? Adjusted right ?
Low compression in one cylinder will increase roughness and it will cause higher IQ deviation numbers . Were the rods from the replacement block checked for straightness?

Are the lifters and camshaft OK ? Fuel filter new ?

My bet is low compression

 

[Scottys248]

Thanks for the reply Dimitri.
I think I remember the garage saying they checked compression etc and it is fine.
Fuel filter is new.
I'll check the other stuff tomorrow but the guys seem to know their stuff...but I wanted to be sure that another injector would be the perhaps the only item needing replaced before getting it.