I'm just a 1500 5.9 98 model. But read this one from a Google search when I was having a glitch. Ran across 1 that sounds like yours (2500 5.9) and perhaps a possibility. Right passenger side underneath is a canister perhaps on yours near the bed. Chase the lines back to the right fender wells under hood and see if Evap lines have a loose connection at the elbows or the 2 lines are bad/loose.
Good luck. R...
Last edited by richmond; 08-19-2013 at 04:20 AM.