I have a 2003 2500 hd 4x4 crew cab w/ 6.0 gas engine. I feel like I am experiencing a power loss while towing. The truck doesn't die all together it just doesn't seem to have enough power to pull. Right now I have a 28ft gooseknec 6500lb trailer attached to it and it barely wants to pull it up a small hill on the way to my house! Any thoughts?