How much horsepower will this supercharger to my a 2001 Ford Lightning SVT?

I have a 2001 Ford Lightning SVT with a Magnum Powers 2.8 liter supercharger with 15 lbs of boost with 3 upper and 10 lower? How much horsepower will this add?

Are you asking how much power that entire blower setup will add? Or are you saying it's at 15lbs of boost right now and you want to know how much power you will get from changing out the pullies to run more than 15lbs?

Much more than the rear tires could ever transfer to the ground.