hi i have a 02 2500 4x4 duramax she has no power and when it shifts down i get black smoke and now she is starting to start hard i am not sure if injectors were ever changed so i am thinking it may be them she has 240,000 on her any help would be great

 

also when climbing a hill i have no power and it just keeps shifting down and smokes like hell black smoke

 

have u replaced the air filter lately ..or changed the fuel filter... cleaned the mass air flow meter or the mas air preasure senser ...is the any codes yet....scott