Pressure gathering in fuel tank

[roman]

You might have two of the lines around the wrong way.

There's the return line that feeds fuel from the rail back to the gas tank, and this sends the fuel back into the BOTTOM of the tank, so its quiet.

The breather line for charcoal cannister comes out inside the TOP of the tank.

So if you get the two the wrong way around, your vapours will not get out of the gas tank, it will pressurise and try and push the fuel out instead.

Also the fuel return line will be noiser than it would be otherwise, as its splashing fuel out into the "air" in the tank rather than the fuel.