Bing carb breather/over flow

When discussing these issues, can we agree that there are no "drain hoses" coming from the carburetors?  There are air-vent lines, and if fuel is coming out of those, that's certainly a problem, probably indicating that the fuel/float bowl has become overfilled.

Stephan, a photo of your setup would be helpful.  It might also be useful to try flying without the electric pump once again and then staying with your aircraft for those next 30 minutes to see where exactly the leaking fuel is coming from.