Engine struggling upon revving, ideas?

Hi all, trying to get to the bottom of this issue. Here's a video. Noticed it recently, upon revving hard, the engine nearly cuts out, never has done, just splutters for a second. It may have always done it, I just noticed it when I revved hard to check for a turbo whistle. Which is now sorted.
I've replaced fuel filter and lift pump, checked lines and coolant piles, had a slight leak on on of the pipes on the thermostat housing. But minimal.
Failed at removing the fuel stop solenoid as it's solid and won't budge, so was going to remove the injection pump to remove it and replace. Will do valve clearances first and see what the throws up and if not joy will remove injection pump to replace solenoid.

Don't suppose by watching the video and reading above anyone has any ideas on a possible cause?

Thanks all

I ont think you uploaded the video, if you did, it's hiding from me.

Col

Ah it didnt upload. I'll add to YouTube and send a link