I noticed that its glitchy when I put the spoiler on my new Banshee.
The traction stat would only show an increase after hovering over the 2nd spoiler. If I backed out of the menu and went back in I could highlight the first and the third spoiler and traction wouldn't change. As soon as I went over the middle spoiler the traction stat showed the increase and then the increase remained when hovering over all three.
I really don't know if this does anything or if that stat just shows glitchy... people have such a wild placebo effect in their minds when they see something like this and then report on it like its fact.
It is glitchy with how it shows up but once any of them are on and you go to remove it you will see the decrease every time. That and it's a huge improvement on some of the cars and I hate how most of them look but as a driver that doesn't like to slow down I need them .