I have an '02 24v cummins high output 6 speed with about 80k miles. I have to let it idle for 15 minutes before driving it or it acts like it's either not getting air or fuel. Even then, when I don't let it idle, it won't go past about 20mph/2000 rpm and spews black smoke which leads me to believe it's an air or turbo problem. Sometimes while driving the problem suddenly appears and the truck lugs at around 2000 rpms. Usually I shift down to 5th (problem most prevalent in OD/6th) and run the rpms a little high until it "corrects" itself and you feel a sudden surge of power as if the turbo suddenly kicks in. The filters have been changed repeatedly with no results and I'm hoping to fix it myself before taking it to a shop to have the turbo ripped apart. Any suggestions would be of great help.

 

Have you checked for codes? Any auto parts store can usually do this for you. Check the boots on the intercooler pipes for leaks or rips or tears.