1.6 lt 4 cyn eng. car starts fine runs for like 5 mins, then it revs up to 3k rpm, check engine light comes on and it slows down to 1k, then it starts to bounce between 3.5k and 500 rpm's. Code flashes 12 once then 13 once and repeats over and over. ECM and the Oxygen Sensor have been replaced as have the throttle position sensor and Idle air control valve. What have I missed? Suggestions?