I'd guess at the engine management light coming on due to the lambda sensors picking up poor oxygen levels. I'd be inclined to vent the pipe to atmosphere & jury rig a small catch tank bottle in which to see how much comes out.
The reed valve seems to be the suspect, especially as the engine ran correctly with nothing else untoward.
Presumably the light will cycle itself out with a few start ups?
Keep you on the road, anyway.
