I had limp mode on my last A2, started after cambelt/water pump change and never did work out what it was. On that car pushing past 3000rpm in 5th, especially up an incline, triggered limp mode every time. On this A2 it only happens occassionally when I push it past 90mph or try to take it to 4000rpm in 4th. As it’s rare I ever want to do this I have been living with it but you’ve inspired me to get to the bottom of it with your incredible perseverance! I think I will get underneath and check all the little vacuum hoses first difficult to see around the turbo area from the top of the engine. Im curous about the exhaust manifold blanking plate - is that a mod or would all tdi 75’s have it? If so could you post where in the engine bay it is so I can have a look? Congrats on finally ending your limp mode nightmare!