Starts right up at the turn of the key and runs pretty good for the first mile or so. Then the misfires and sometimes backfire begins. Of course with that comes loss of power and just plain poor running. I replaced the plugs, coils, mass flow sensor (mechanic recommendation) cat converter, valve covers (oil leaking on plugs), PCV valve and inspected the wiring for any signs of damage and proper grounding. No improvement at all. Another mechanic told me the P300 code almost always requires a new ECM to correct the random misfire at a cost of appx $500+ (300 for the ECM and 200 for the dealer to program it. That does not include labor to replace the unit. If I knew for sure that would fix the problem I would go for it, but that's a lot of money for a maybe. I'm looking for some feedback from the group to help me decide. Thanks.