I have a 04.5 lly with 154,000 miles. a couple months ago I started noticing a pecking/knocking sound while accelerating. it doesn't do it all of the time, seems like it starts at about 1700 rpm and continues until the truck shifts gears and rpms drop. once I'm at cruising speed it stops, or I can't hear it anymore. would this be the cp3? or could it be injectors? I have no idea, but I figured this would be a good place to look to see if anyone else has encountered this problem.