I have a 02, F-450, for awhile it had smoked blue, white smoke until it warmed up, I mean as soon as the temp gauge moved it would quit smoking and run fine. However the last two days it doesn't want to come out of its funk.. It starts fine an idles good, but no high idle, that hasn't worked in some time.. It fights to get over 2000 rpm has no power and is sucking down fuel. It went from 13 to 5 mpg. It's my service truck and weighs 12,800. Any ideas? Seems to be getting plenty of fuel, it just reakz of diesel out the exhaust when idling cold. I don't hear my turbo spool up either. I'm thinking my exhaust back pressure slave is stuck, not sure though. Would appreciate some help!