Troubleshooting limp mode: "Control difference - intermittent"

Well done and I bet you had a smug grin when you finished!

Yes I did, a smug grin on my sooted up face and clothes. Thank you Doctle for your help.

I need to get the return pipe sorted for oil leak. I should have sorted it out when the turbo was out but I didn't know the pipe could have been removed at the engine end. I think I need to unscrew the banjo bolt from the engine end, remove the pipe, clean it again and re-fit it.

Would a silicone grease help for better seal, or is silicone bad on places near oil?