[Veek]

As mentioned, it's probably your carb innards that were wet with fuel when the car was running that are evaporating. If you topped off the car it may also be slosh on the interior of your cap. See if it's wet.
But to be sure, check all of your fuel lines and I'd feel under the car under each fuel cell to see if your cell is leaking. If so, you'll need to inspect the cell and repair. For the breather, my engine also had water hose installed instead of emissions hose and that degrades over time and leaks.

Good luck!