Gilly- Sorry about the "E" - I have owned the truck since 5K miles. The problem has been recurring since about 18K. MB replaced rocker arms, lifters twice and has done full carbon cleaning. Their best explanation for me was the brand of gas I use, but as I stated prev., I only use 93 or higher octane, mostly Shell. I'm not sure what else to do to correct, this, and I get the impression that MB doesn;t either. Any suggestions are much appreciated.