Some, but not dramatically unless you are idling for an extended period, say an hour or more.
The color of paint does not affect gas mileage in any way.
Yes, the faulty power steering pressure switch does affect the gas mileage. It will give a wrong reading of the gas mileage. It is therefore important to fix it when it is faulty.
Yes.
If it is malfunctioning it can affect fuel mileage.
Yes. Yes it does!
yes
YES YESYESYESYESYESYESYES
incorrect tire inflation
the lower your rear axle ratio, the worse your mileage.
All of the engine sensors can affect fuel mileage.
Yes.Yes.
yes