LR TIME (YouTube channel) have two videos about Restricted Performance. Their fix cost nothing, although it took them 4 weeks of work to find the problem.

Chris. L405 - 4.4SDV8 Vogue
P38 - 4.6V8 HSE
Land Rover series IIA V8

Hi Chris,

Yes been watching that in the hope it showed what my problem was…. But unfortunately I have a different code and I did double check but all ok on that front…

Apologies for the delay in replying – the short answer is yes, eventually having swapped everything out and having a massive fight with the warranty company who eventually relented (there’s another story there if anybody is interested).
Car then sold as being off the road for six months for various issues in a three year period was unacceptable to me. Ironically, the new owner has probably got a properly sorted vehicle. 🙈
I’m currently tempted by an L322!😉

What was the fix in the end you haven’t said 😂