Overboost could also be caused by stuck-closed wastegate on turbo. Plenty of threads on here involving mole grips and liberal quantities of WD40
Thanks Joojar.

Yes, I’ve had this off, drowned it, freed it off and refitted. It seemed mechanically ok.

I’m trawling through related threads looking at relevant pressures I should have.

I’ll get Hawkeye plugged in to see what is going on.
 
Thanks Joojar.

Yes, I’ve had this off, drowned it, freed it off and refitted. It seemed mechanically ok.

I’m trawling through related threads looking at relevant pressures I should have.

I’ll get Hawkeye plugged in to see what is going on.

Definite progress of sorts...

As @joojar @sierrafery and others have said, I looked at the actual waste gate. I got hung up on what I now know is the actuator (with big spring in). I found a vid on YouTube which I’ll post a link to shortly.

My waste gate was definitely sticking, but after half an hour of wiggling and lubing, it isn’t sticking any more.

Test drive - Much better, no dip in revs/flat spots.

Not so great news, I did the gearbox test as suggested by @sierrafery, to find it revs at circa 3600, indicating slipping clutch’s.

I’m only ‘half way’ through the gearbox service, so will refill will Lucas Transmission Fix, to see if it helps.

When I’m finished with this and reached a conclusion, I will list all works done, as I have done quite a bit, found quite a bit, and learnt a lot along the way!
 

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