I have an 08 with the 6.4L. I have a knock that nobody can find. It has been doing it for about 15,000 miles. The engine has 200,000 on it now. It is the #8. Engine runs like a top, nice and smooth. All drivers side injectors are new, heads have been off, new lifters and rockers installed. I have no codes. The #8 does have low contribution but not low enough to toss a code. I am getting very tires of the noise and I believe it is getting worse, but it does sometimes almost go away. Very frustrated. Any ideas??