Mufflers As Part Of The Vehicle Body
And as you put the engine into say, a family car, you want it to be silent, but when you put the same engine into a more sporting car you want it to be loud, as that single change can make a significant difference in how competitive the car is in it's class.
But that change unfortunately is tied to the engine itself, which requires you to change mufflers each time you switch to a different car.
I suggest making that option separate from the engine so that we don't have to keep switching everytime we load a different type of car.