Freelander 1 Td4 Engine 'surging' at 1650 - 1750 RPM

Have mentioned this before, but this is getting slowly worse, feels like a misfire but only when 'pulling' at the above revs. Speeding up or down a tad stops the problem. No fault codes logged.

If I remember correctly this is about 'turbo cut in revs' ?? Is it a sign that the turbo is groaning? 150k miles on this one.
Vacuum pipes seem ok. Any other ideas please.

Some garages use 'turbo cleaner' - any idea what this is and how you use it?

Is the boost solenoid doing its job? Check the turbo vane actuator moves freely back and forth as well.

Unplug MAF and see if it improves? Clean MAP?

Lots of things to go through before blaming the turbo itself - what about a diagnostics plug-in?

I sometimes get a surging at those same revs. It's very random, so I just ignore it tbh.

I do as well, but when free-revving, not under load.

But yes, this could be one the OP will be chasing forever.