Bob, no answer, just "newbie's" question here: Are you referring to the saw tooth pattern of the torque curve?
I am calling a flutter.  

Kidding aside -- is it not the clutch slipping? Or I assume from title of thread and the AFR curve, something "bad" happens at 5400 rpm? The sudden drop implying something "mechanical," not software related?


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Regards,
Can
997 Turbo + Bilstein Damptronic "Stage 2" ( Review ) + GIAC ECU Tune ( Fast as a torpedo & reversible to stock - Review ) + Cargraphic Exhaust ( Oh heavenly noise! )