It was worth 1 or 2 tenths on the 2g consistently. I logged temp drops from 110 with the light in to 80 with the light out (on an 80 degree day). I had it set up so there was only the top bolt and one side bolt holding it in, so it was a matter of 20 seconds to remove or install it. Easily fit into my 20 minute routine at the track.
Not the best for aerodynamics, but the result was still a net gain in performance.