I've been doing research on many fuel saving devices and the only company that I have found that has any independent verification of there claims is a company called Vapor Fuel Technologies. They have a system that has been independently verified to get a 30% increase in mileage on a 2006 F-150 running the EPA Highway test. Looking over their site, they plan to have retrofit packages for most trucks and SUV's in 2009.
I like seeing a Mustang as an R&D vehicle! Itís just too bad some people make these claims unverified and ruin it for the folks that actually have technologies that work. GM, Ford, and many other Auto and College institutions have HCCI and auto ignition engines, GM released a HCCI car last year.