I'm curious about the weight differences too. And yes, all PP1 wheels are staggered: 19x9.0 front, and 19x9.5 rear, with 255/40/19 and 275/40/19 tires, respectively. As a side comment, I think there's a PP1 model that has the same tire sizes, but wheels are 1/2" wider front and back. It has to be the base Mach1, no? There's only the Mustang PP1 and Bullitt, AFAIK. PP2 cars have wider tires and wheels.