Shell and Kroger 87 octane causing detonation

[ford250]

I have a custom tune installed on my corvette. The person who I did the tune with, who is very well known in the LS engine tuning world, was very firm on not using Shell gas when doing the data logs for the tune. He said he has seen it hundreds of times, in the logs, where the engine pulls timing back when using Shell gas under WOT conditions.

He would be correct...Shell is not a gas tuners use. In my area the dyno shop claim they typically see better numbers on 93 octane from QuickTrip