Just to clarify, my explanation above does not disagree with Sideways' gain of 16hp. An explanation for the gain would be that his car is optimally tuned for a fuel somewhere between pump gas and 100 (and up around 500hp everything gets exaggerated, so I'd agree with a 16hp gain )

Sideways, FWIW do you have data from your latest tune to share?

 

^^I was the only disagreer on this thread before you came!