I have a 2008 G6 GT convertible and I'm having a problem with random misfiring on all cylinders. I have changed the plugs and plug wires but the misfire is still there. I can feel it at idle and with mild acceleration. I have clamped an induction timing light to each wire and there are just random misfires across all. I am thinking the next step would be replacing the coil pack? Any knowledgeable input would be greatly appreciated.