Sethodine
Elio Addict
It was probably changed for aero reasons. I'm no engineer, but I know moving air hugs close to convex surfaces (known as the Coandă effect) which was probably creating a pocket of pressure behind the curved skirt of the P3. By going to a kammback design, they eliminated that extra bit of drag and probably improved the milage by 1 or 2 MPGs.