i found a Combo that UPR is running right now... its "UPR COLD AIR INTAKE UNDERDRIVE PULLEYS 96-00 MUSTANG" for $159.95 and i didnt no if the 4.6 responds to pulleys vary well..
Won't feel much but you will feel a little more pep out of the engine. I got these and deleted my A/C dummy and some other pullies at the same time. Seems to be a bit torquier now.
Piggybacks are the type that bolt to the original dampener. Some of the pulleys are all one piece. I think they give you a slight gain in power with the underdriven speed of the Alternator and accessories. The real gains are better if you delete the dampner. I did this and they do it all the time on my Mazda MX6 V6. They have a dampener from the factory as well. The rotating assembly on the 4.6 is is internally balanced just like the Mazda motor. I have had many disputes and a did a thread about this. Had a guy say that ran 2 GT's for over 50000 miles without any problems. I had owned 2 Mx6's and on my 3rd all with Underdrive pulleys and no dampener. (In between I owned a 97 GT and looking to get another Stang.) I have logged now 225000 miles without a problem. The increase in power to the wheels is taking the weight off the rotating mass like a lightened flywheel.