As title say p0306 cyl 6 misfire. Only misses for about 15-20 secs and only after setting over night. But it will eventual turn on check engine light. 168,000 miles new plugs and Chrysler wires 6 months ago. Replaced number 6 plug and wire again. Ran wire over intake plenum. Have checked for vacuum leaks get no hint of a leak. Went so far as to plug off the brake vacuum line. Still a miss for a few seconds only on a stone cold start. Did a power clean on the injectors. That did keep the light off for about 3 week. After the initial start up miss it runs perfect. I am pretty much at a loss. Any ideas. If I do have to pull the plenum I will put in new injectors. I do have a new coil pack may try that. Any ideas