give some wd40 where the wastegate rod meets the turbo and push it toward the turbo few times as to see it returning freely back to the valve, it doesnt move too easy cos the valve's spring is quite heavy but if you grab it with pliers it must move both ways...the tester reading has nothing to do with the machanical side it shows the modulator's duty cycle...aren't the turbo hoses delaminated? (they should be quite hard not soft)

Update: Problem still there, not getting any better. Garage thinks it may be fuel pump on way out so are going to do a fuel pressure test.

Current symptoms are lack of power and black smoke on acceleration. Worse when engine cold. Slightly rougher running, especially on acceleration. Crusing is fine.

I'm not so sure though...I remembered an additional detail - the problem first occurred just after I suddenly took my foot off the accelerator whilst moving through water (only about 6 inches). I remember thinking there was a bit of a strange noise/clunk at the moment I did this, and I put it down to the water. I'm wondering if the sudden vacuum in the intake manifold could have broken my EGR valve (is it a butterfly or something at the manifold?), causing it to be constantly open. (I've been getting intermittent error codes about EGR stuck both open and closed)

Is there a way to test the EGR butterfly valve to see if it is stuck open? Or, is it a difficult job to remove it and visually inspect it?

(My turbo seems fine btw. Wastegate movement is fine, reaching full boost ~230kPa. Felt the pipes, feel firm - don't think there's any delamination)

Thanks!

As I said before blank the EGR off. It is total crap

Yep, most people who've done this seem to report improved performance without any negative consequences. Might give it a go.

For now, can I just remove the engine cover and unclip the intake manifold rubber air hose to visually inspect the internals of the EGR valve?

The EGR was closed when I inspected it. Covered in soot but not too bad. The turbo hoses all feel fine, no obvious defects.
I checked the red ECU plug and it was FULL of oil. Spent 30 mins cleaning it out by spraying contact cleaner into each individual hole and shaking it about.
Cannot tell if the problem has been fixed yet as the engine is quite warm and the problem manifests mostly with a cold engine.

Will attach some pics of my dirty plug and EGR...

Replace the injector loom ASAP, cleaning the plug doesnt fix anything only improves things a bit for short time