Gas does make a difference, especially when your tuned.
I run 93 with my tune.
My old car was a genesis and I actually lost power running 93 because the car was tuned stock for 87. It was a difference in only 4hp so it's hard to see how you dropped a tenth of a second.
IMO you probably noticed time difference due to weather or track prep rather then gas.
I would run 93 as it burns better
Use code : gator
To receive 5% OFF
2011 5.0 --JLT, Bama tune, steeda WP pulley, tracklight 18s, stallion LCAs, stallion pan hard bar, cat-resignator delete, X pipe, magnaflow mufflers, Eibach springs, 3D carbon spoiler, barton SS