Do M5 Aero kit's fit on the 540i or is is wider or somthing? If they don't fit then how much of a difference are we talking here? If they do fit, why don't many people get the AC Schnitzer M5 Aero upgrade instead of there lame BMW factory upgrade looking kit. Bekkers makes a M5 Uphrade for the 540i but I love the AC Schnitzer M5 upgrade. Any help would be great.