Exaust and dash lcd

[hallow]

Firstly does anyone know if the fuel consumption is just an estimate from a table of rpm values or is there actually a flow meter on the fuel line.

And I have an 06 Focus which has an oval sports muffler on it but you still can't really hear it only when you floor it and it gets around mid rpms at which it can still be hard to hear over the sound of the engine itself. What would I have to do to get it more audible?