Better Gas Mileage?
#6
Such as under drive pulleys, CAI and gears ( Depending on if you drive hwy or in city)
The less the motor has to work the better.
#9
doing the bolts on can help fuel milege if you drive conservatively, but honestly, who buys all the goodies and drives like their grandma? in theory you could probably save fuel but i doubt you will in the long run, for nothing else other then loving the sound of a v-8 running through the gears.