Now that I see the scale more clearly, it's probably not from the Audi. It's got the pressure regulator and diaphragm assembly attached to a valvebody with pressure crimps on the pipe ends, so it's definitely a wastegate/pressure regulator for a forced induction system. Could be for a small turboprop aircraft engine, but now I'm leaning more towards a diesel truck motor. I've even seen similar pressure wastegates on cruise control systems, albeit smaller.