it loses power,idles fine but when acc, is pressed gets very rough ,the rpm's wont go over 2,000

i have a 2002 ford f-350 turbo diesel. it will run fine for a couple days then run like it is out of fuel.it will idle fine but wont go anywhere..i have replaced fuel pump,filter,cleaned fuel tank & lines, map sensor. i was told to try the crank & cam sensors. it loses power,idles very rough,the rpm's wont go over 2,000