So the hotter type plug does a worse job. Interesting... I will have to think about why this might be.
For clarification:
Were you running Water injection?
Was this completely under boost, or did it exhibit the same behavior under vacuum/idle?
I have seen mileage improve by changing heat ranges, but I thought I went to a hotter plug to improve the economy. I apologize - unlike your awesome data acquisition systems, I have to rely on my ever-more-sketchy memory.
I will think about what would cause this and post again if I can think of something.
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1986 GXL ('87 4-port NA - Haltech E8, LS2 Coils. Defined Autoworks Headers, Dual 2.5" Exhaust (Dual Superflow, dBX mufflers)
1991 Coupe (KYB AGX Shocks, Eibach lowering springs, RB exhaust, Stock and Automatic)
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