A great way to free up some engine HP is with an under drive pulley.  The under drive crank pulley manufactured by Unorthodox Racing has been dyno proven to make 12 RWHP with a cat back exhaust and an air intake system installed. 

Not only is RWHP gained by under driving the accessories, but rotational mass is also reduced.    The stock crank pulley weighs 3 lb 15 oz.  compared to the Unorthodox pulley, which weighs a mere 1 lb 9 oz.  I haven't experienced any problems so far with accessories being under powered, such as alternator, AC, and power steering.

Not only is the under drive pulley a performance gain but it also increases the life of your water pump and alternator.  Therefore, it can be classified as a reliability modification as well.

 Overall, I'm happy with the purchase.  Where else can you add 12 HP to your rear wheels for around $200?

REMOVAL OF THE CRANK PULLEY BOLT 

Removing the bolt that holds the crank pulley in place is not an easy task.  I was told it takes approximately 400 ft lbs of torque to break this bolt loose.  Even if you own an air compressor, most household air guns  are not capable of 400 ft lbs of torque.  It took three of us to remove the bolt.  One to hold his foot on the brake, one to hold up the hood as high as it could go, and one to torque the four foot steel pole.  We simply slid the pole over top of a 1/2 inch drive socket.  It is very possible to break an engine mount while torquing the bolt loose, so be extremely careful.  Engine mounts aren't cheap!  After about an hour or so of making sure we were going about this the correct way, I began torquing the pole until I heard a snap.  Luckily it was just the bolt which had broken loose.  This is a standard thread pattern (left-loose/right-tight).  After that, everything else was easy.  The new pulley installed only one way, so there was little to screw up.  It took a little trial and error to find the proper belt size with new pulley so I'll same you some time and list the ones which worked for me.

W/O Air Pump -->  28.0 inches ( 5 rib)

W/ Air Pump  -->  To be determined

Approximate Performance Gain:

Under drive crank pulley - 12 HP at the rear wheels