The thing with aero upgrades is that unless your hitting speeds over 100mph their effect is minimal at best, they look cool, gives it that race car look. The only way to to get aero that works is to do a lot of wind tunnel testing, and your talking really big money. I highly doubt that any of the companies that sell aero for our cars have done any R&D. They most likely copied JDM parts and adapted them to fit the Fiesta platform. Most likely the best aero for any street car is hood vents. They let the trapped air out so it is not pushing on a flat hood panel and they also let the heat out so the engine bay stays cooler.
