Hey guys,
I was surfing the jegs online catologe, and they have a section called save gas-go fast.
There is a list of parts, and one are aftermarket pulleys. Do they really help gas mileage or power? Ive been wondering. Feedback would be great. Thanks alot.

By decreasing the diameter of the crank pulleys and/or increasing the diameter of the accessory pulleys, you will cause the acessories to rotate slower. This WILL increase the max power available to the wheels.

It will also save gas, as most of the time you don't NEED max power to the wheels.

There is one additional thing to keep in mind. When you slow down the accessories, you might cause them to be spinning too slowly to operate properly. This might cause the engine to overheat (water pump spinning too slowly), the battery to die (alternator spinning too slowly), or the A/C to not cool well enough (compressor spinning too slowly).

I would only consider changing the pulley sizes if the rear gears have been changed from stock. GM selected the pulley sizes for the expected cruise RPM of the engine, as configured from the factory. Unless you've changed the cruise RPM, the pulleys are probably about as good as you can get.