I have a 1992 Ford 2wd F-350 with a 5.8 motor that is running rough and blowing black smoke. It has new cap and rotor, new Champion spark plugs, timing is good, no vaccum leaks found, all sensors seem to be working, no check engine light, cylinder compression are all around 140lbs, fuel pressure is 12 primed and 40 running, air filter is new, any ideas why it is running rich?