And like I said, it's probably (with lets say 80% certainty) not even the problem. I HAVE replaced some valves, it's not like it's an impossibility, put a plugged pipe is more likely the problem.
If you activate the valve (which is possible either by using the "activations" screen with their computer or by applying vacuum directly to the valve) the engine should almost die. If they apply vacuum to the valve and almost nothing happens, the pipe is plugged, simple as that.

Gilly