I'm having the same issue on my 07, put a new used motor in. Took it for a drive and the check engine light started flashing. Got the p0300, p0302, p0303. The plus are new (bosh), new plug wires and a new coil as well as a new catalytic converter and gas cap. Had the dealer look at it, the tech relearned the computer and ran the car with the, then came to me and said try different plugs, he recommended AC Delco, but I told him NGK plugs are what was in the original motor, he also said that there is no physical sign of the motor misfiring, he said he believes the computer is giving a false misfire. so I put in NGK plugs and went for a drive, check engine light still flashes. At this point I'm out of ideas of what to do