well. it must add something!
enough to make my puny 2.5 L 8v beat an S2 and an S at a certain auto-x.....

 

Mine is going on the 1/4 glass, driver's side (one on each car). I'm getting a very light tint done one the windows first (just enough to help save the interior, maybe a 40% transmittance). It'll be soon enough.

 

John D. said it adds about 30hp. The little decal adds 20 hp so I have a 50hp boost.