Blueish smoke at start up and shift
 

Sorry if the title is kind of vague. My truck is pretty much stock except for an airaid intake as far as I know. I've kept up the oil change to every 3000 miles. When I bought it at the dealership in February they put cats back on and an EGR. When I started my truck in the morning on sunday and I noticed puffs of blue tinted smoke coming out but stopped after about a minute or so. When I drove off it started doing it again then stopped after I drove about 150 feet. Then today I got on the highway and when I tried getting up to speed it felt like it got stuck in a gear. I looked back and it was blowing quite a bit of the blue smoke. I let off and then it ran like normal with no problem. I've heard it could be that the fuel filter is due or I need new u joints. I had the dealership replace the fuel filter about 6000 miles ago. This is my first diesel. Total green horn. Any help would be appreciated.

well, for starters i am not sure where you got bad u-joints from. if you think that could be causing it go ahead and rule that out.

Now, on to your issue; blue smoke is oil. so if the smoke you see is blue than that is indicating somehow you are getting oil into the combustion chamber. this can happen in alot of ways, it does not sound like you are having major compression issues. you can get oil down through the valve seals leaking down past the seats. i have also seen heads cracking on 6.0 diesels which has sometimes led to a similar situation.

how does the coolant look? anything in the oil?
check all of your fluids, see if any are down and make note of it.

Let us know what you come up with