I have an 04 early build with 200k, I got it when it had about 140k and it ran great I tow a 4k enclosed trailer which should feel like nothing even is behind me which it used too even when I would go up a steep inclined bridge I could maintain 70 with no problem at all. Since then I had a cold start issue and had it in the shop for a while until they finally figured out it was the FICM and had that changed other than that I have just done general maintenance oil, air filter and fuel filters, well anyway ever since I got it back it just does not have the power that it used to have. I will loose speed going up a bridge without even having my trailer not really bad but enough for me to need to give it more fuel. If I have my trailer hooked up it will loose a lot of speed until it hits the passing gear and when it goes into the passing gear it sounds like its sucking air real bad behind the glove box where the turbo is. Also I don't know if this is related or not but when my truck is running and I am hooking up to my trailer I am close to my exhaust pipe and It sounds like it surges. you can't hear the motor make any changes in rpm's or anything you can just hear like intermitent changes in tone coming out of the exhaust, maybe this is normal I don't know. Thanks in advance for the help.