My 2007 A3 3.2 quattro has a leak at the fuel pump, seems to be the right/passenger side unit. The engine doesn't have any problems running and before I replace the whole unit I'm trying to understand where exactly the leak is. The main symptom has been a gas smell inside the cabin when I drive. Dealer has confirmed leak at the fuel pump.

I'm not sure exactly what is supposed to seal, and where. I ran the engine for about 5 minutes with the plastic/rubber cover off the pump to see if I could observe it leaking. The only thing apparent was some fuel bubbling in the little open-topped nub on top of the pump. What is that thing? Is it supposed to be open? It doesn't look like there is anything that is supposed to connect to it (alldata images show nothing attached to it and make no mention of it). I see a similar nub in other images of the unit but cannot tell if it is supposed to be open on the top. Is it some kind of vent? When I put my finger on top while the vehicle is running, it got wet with a little fuel. So is that the leak or is that supposed to do that, and it's supposed to seal at the (rather loose) plastic/rubber cover?

Video of the bubbling is attached (ignore the noise - lawn work in background).
Here's another image of the nub I found online - from someone else's car with a fuel pump leak: https://cimg2.ibsrv.net/cimg/www.aud...eak-183838.jpg

Thanks