hey guys im a noob here, but I did read in a tech article about poor fuel millege on a 7.3 powerstroke and it was due to the copper o rings on the injectors. I think Marc was the poster of it. I have a 99 F250 PSD 7.3 have had it for a year, truck runs perfect never had a problem except 10-11mpg. I have added 4" full exhaust, Diablo Sport chip, then switched to SCT X cal 2, does not matter still same exact millege each time. Like I said starts up every day , no smoke coming out at startup or during regular excerating , of course when I gun it she puffs out like a normal diesel. So I am going to try what he had posted in the tech article about checking fuel pressure on rail at start up etc, he said he went from 11mpg to 19mpg after replacing the copper o rings. Anyone know if the process of replacing them is too much for a moderate mechnic ability? Thanks...