I'm curious to know how many of you that got too carried away with a fuel additive and it caused your CEL to come on? I did this on my sons 5.4L.. The code showed to be a miss fire.. The 5.4L had a slight shake at idle while light was on. Cleared code put 11 gallons fresh fuel in. Drove 10 miles on highway light stayed off. Idle shake is slightly noticeable now. No more MMO & TC-W3..