Q - 2010, 6.4. When passing vehicles, occasionally will sputter and white smoke real bad. Power is reduced and have to back off the throttle. The Regen is NOT on during this and can usually give more throttle again and not happen. It does it about 1-2 tank fulls. No lights come on either. Coolant doesn't really drop. Any ideas?

A - When you go full throttle to pass, the EGR valve will sometimes open.  My guess is that it is hanging open and causing the problem.  It may be a good idea to pull it out and take a look at it to see if it is clogged up.  The egr valve will open and close on regular intervals without the truck doing a regen.  I would check for codes to see if maybe there are any other hints in there, but that would be a good place to start.