Ok some back-story to my problem. last week a spark-plug backed out after 15,000 miles on them and in the process of backing out it took all the threads with it...Got it helicoiled. Thought that was the end of engine trouble. NOPE! after driving it i couldnt tell the difference..little bit off top end according to a G-tech(never really accurate anyways) Running wise it runs ok but if i get on it at wot it bogs down about 4500. and then starts knocking and idling very rough. Throws no codes. Turn it off, restart and runs fine and dandy. Wot it again and it goes through the power band fine and dandy. no knocks no sputtering no problems. I changed the fuel filter. Compression test was ok. all plugs are good too. any insight to what this may be would be great. I am trying to exhaust all options before i tear the motor down and flat out replace the head assembly. 