06 jeep commander 4.7 p0300 and p1128.

I have a good head scratcher. 06 jeep commander with 4.7 150k. After I let it sit for a few mins, and overnight. i am getting a p0300, and p1128. it only misses under first load. and as soon as it quits missing, (> 50 feet) there is more misfires. new plugs installed 500 miles ago. during normal driving my soils is showing closed loop and there is a normal waveform pattern. consern acquires wean cold and at operating temp. Thanks in advance