Using a higher octane without getting a tune is not only a waste of cash but can cause build up deposits that your engine can't burn. Which will lead to needed to run this octane to keep it from dieseling (running after shutting off the ignition)in the first place. (Deposits form causing hot spots, and pre-igniting the fuel before the Spark plug is suppose to.)Called detonation or pinging.
Remember Higher octane gas actually burns SLOWER or cooler then lower octane fuels. Using this will cause the fuel that is not being burned to build up in your heads,valves,pistons, etc...... So the trick is not what you think is best,but actually matching the octane to what your timing, ignition, and engine can actually burn in the compression stroke.
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Mods-MAc CAI , True Dual Flowmaster 40,3.73 ,T-Lok, 25% UDP, 3/8 Phenolic Intake Spacer ,Steeda Tri-ax, SCT Chip/ Tune