Fuel Filter Change

[I know notihng]

Afternoon,

I have just changed the fuel filter on my Golf mk4 TDI 150, it all went well and car started up no problem but now i have noticed a 'filling/woosh' sound when i turn the ignition on, also after turning the engine off there is a squelch sound as if air/fuel is being trapped.

Any suggestions as to what it might be? I have attached a picture of where i think the last sound is coming from, the 1st sound sounds like its from under the drivers seat.