My car struggled to pass the MOT, and with a bit of investigation it seems that the vacuum was not regulating the valves in the inlet port properly. I inspected the system and the vacuum pipes seem fine. I then disconnected some of the pipes and checked the vacuum actuator on the inlet manifold by hold it in a different position and cover the port with my finger. The actuator held, then returned quickly when I uncovered the port. So far so good. If that had leaked, new manifold! Next I looked at