Should you “top off” your gas tank when filling it?
No,
Why might you ask…
It can damage your charcoal filter, pressure builds in the tank and floods the carbon vapor collection system
Also at the gas station there are vapor recovery system so that if a tank is full, the pump will pull the extra gas back into the stations tanks. This is a safety precaution to ensure vapors will not escape into the air. (kinda of like throwing away money)
Car’s exhaust system consists of tail pipe, muffler, catalytic converter, exhaust pipe, headers?
Yes, in fact you may have multiple muffler (up to 2) and catalytic converters (up to 4).