Be very careful, about running the engine. The fuel could ignite by the exhaust system.
It sounds like the vent is leaking? Do not overfill.
If it is the high pressure line, to the engine, fix immediately.
The alladata website has some info on the fuel tank, under
. Fuel Delivery and Air Induction
45 Filler neck
46 Fuel tank air admission line
47 Fuel line (shuts off nozzle when refueling)
75 Fuel tank
77 Activated charcoal canister
88 Fuel delivery module
89/1 Left closing plate
92 Fuel pressure line to engine
93 Purge line to purge control valve
B4/3 Fuel tank pressure sensor
M3 Fuel pump (FP)
Y58/4 Activated charcoal canister shutoff valve