had the same issue... they had it in twice and replace all coil packs... i lost faith and tracked it down myself.
turns out one of the contacts was not making good contact with the coil plug.
you can test it when the car starts misfiring, pull right over and keep the motor running. open the hood, juggle each connector and see if the miss stops.
i was going to buy new connectors and replace them, but they dont sell em... the whole harness is ridiculously expensive.
to permanently fix for free, pull the connectors and take a small screw driver and pry the connectors closer to the top so they can make good contact with the blade inside the connector.
You will see the metal tabs in the horizontal slots... just pry them out a little bit and plug them back in.
good luck.
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