After you get the single flash, wait 2 secs and then hold the button 6 secs..then turn off key for 50 secs , on for 10 and then restart.
That will reset the HFM memory to mean..then drive the car for a couple of days for it to re-adapt see how it then runs ... and then check if any codes come back on 8 and 14.
The big power change at rpms comes from both the variable cam advance and the runner length change as rpms increase..you are aware of that????

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A Dalton