[Stanger98]

underdriver pullies don't hurt anything on the vehicle CFG. This is coming from an ASE mechanic. They slow down the accessories being run on the drive belt (a/c, alternator, etc.). The only effects is that the a/c doesn't blow as cold as it used to (usually not THAT much of a difference) and the alternator loses a little efficiency. As long as you don't have a high power consumption sound system or something of the sort, you will NOT have one problem. And UDP's increase horsepower by freeing up the crank from more load from the accessories, they increase fuel efficiency by slowing everything down, so you could run the a/c without losing any efficiency whatsoever.