Originally Posted by kscoyote
1) you will feel a difference past 2500 RPM especially, as the faster the engine turns, the more power the accesories rob from your system. When trying to pass someone on a 2 lane, you'll notice you can get around other cars much more quickly.
2) You won't necessarily fell a big difference in everyday city driving, but if you time 0-60, and especially 1/4 mile, you'll see a big difference, as MustangDewd did.
3) You'll see a 2-3 mpg gain on your gas mileage, especially at highway speeds for the reasons just described, AND it will extend the life of your accessories (alternator, power steering, water pump, AC compressor, etc.
4) It will NOT affect the sound of the engine, except to make it a bit less noisy as far as belt/pulley whine. Exhaust sounds are affected by the mufflers, not anything in the engine bay.
5) It doesn't "add" horsepower, it frees horsepower that's used to power your accessories. So, the hp at the crank is unchanged, but the hp at the WHEELS is increased.
everything you said is correct except for the part about HP at the crank. The HP at the crank will increase because you are making an adjustment to the motor. The only time you gain RW HP and not Crank HP is when you make an adjustment to the powertrain behind the flywheel (tranny on back). eg. Adding a cold air intake will increase HP at the flywheel and the RW's, but swapping out your 3.27's for 3.55's will add HP only at the RW's.