6.0 Clutch/Power Help

[fallwater08]

I have an 05 F350 6.0 with manual trans. It has about 47K on the odometer. It doesn't seem to have as much power as it should and I took it to Ford to have it checked and my tech said that it was fine and the Manual transmissions just don't have the power that the automatics have. I still think I have a problem somewhere because when I first start the truck, I can't pull the slight grade of my driveway in first gear. I have to put it in L or I won't make it 30 feet to the flat part of the road. Once the truck has been driven and is warm, it seems to be fine. Also, I've noticed some shuttering in the lower gears (1,2,3) at times with no load. I'm not sure if anyone else has experienced these issues or not. I bought the truck with 34000 miles on it so I am the second owner, but this problem just developed. Also, it seems to lack power with regards to the 6.0 auto I had and the 7.3 manuals that I owned in the past. Any ideas of where to start?