That's a good question and it sounds like you've already checked/replaced anything I might suggest but best place to post that where you can get some good help is in the help section for your year truck/engine size, here's a link: http://www.ramforumz.com/forumdisplay.php?f=172 but good luck!
Thanks for the welcome folks.
I do have a question maybe someone can answer. I ust had the 5.9L gas engine replaced in my Ram 2500 4x4 auto trans. This thing shudders right off of idle and uses gas like it's going out of style. What has been replaced besides the engine is: complete tune up, crank and cam sensors, alternator (136Amp), fuel pump. The distributor is in synch and there are no codes present. Any thoughts or ideas??