Ficm or glow plug system?
 

I have a 2006 6.0 with 110 thousand miles if i let it sit a couple days it starts hard and idles hard let it warm up and it will rev up by itself. has no power if you dont let warm up and if you floor it its a cloud of black smoke what is wrong with it

we need more information to tell you anything, do you have access the correct tools to look at the ICP pressures/Balance tests ect?
or are we working with no decent scan tool?

What do you need to know and no this is my first diesel not to exp.

I don't think it's the glow plugs...