Got a 99 GT, had a problem with a high speed misfire , replaced coil packs and plugs. When you rev it up it goes smooth until 1800 picks up a miss all the way up to 2500 were its really shaking the car. No codes or MIL light but code reader reads pending ING coil F circuit malfunction. Replaced that coli with another and no change in the way it runs.. Checked power to coil and pulse from PCM both good what else could it be??