i have noticed a slight rattling noise under acceleration, if it was a gas engine i would call it a spark knock. engine runs fine, no loss in power, has new Bosch injectors. im not sure if the noise started after the injector change or not, before injector swap it had a lot of injector rattle and that is all i noticed. Not sure what to do, i am going to have the valves readjusted and see if there is any change in the noise

 

How many miles on the truck?
If valve adjustment doesn't help, you may want to run some 2 stroke oil in the fuel. It is something cheap to try and I know some people have said it helps with injector rattle. Mine seems to be a little quieter when I run it.

 

I have the same noise and there has been LOTS of posts about it. Most say its just fine. Does it go away as soon as you let off the accelerator?

 

Had a similar issue. Mine was the transfer case. It was dry and the chain kept slapping around in there. Drove me nuts. Stuff in your transfer case moves around even in 2wd.