I have a 07 with 40,000 miles on it, and when I let it sit over night or all day while at work it is very hard to start. It will crank for a long time before it will actually start. However, if I drive the truck for a while, shut it off, and then try to start it, it will start just fine. It doesn't sound like it is having a hard time cranking at all, but cranks a long time before it will start when the engine is cold. I recently had the fuel filter changed the problem stopped for about a week and then came back. Anybody have any ideas what this could be?