I've got 4" straight exhaust (no cat/muffler) on mine and it does the exact same thing. But its very clear faint greyish white smoke. It smells only like strong rich diesel exhaust. I would imagine this is entirely normal since there is no restriction whatsoever ( especially cat being gone) on the exhaust, and being a diesel. If it smells like coolant then you have a problem, but from what I've heard from numerous sources, I believe its typical on a diesel to have atleast some smoke being straight piped. Of course, it also could be running rich, hence the reason guys with tuners click em on and blow thick black smoke due to injectors dumping way more fuel in the cylinder.
'05 F350 srw 6.0
325x65x18 Nitto Terra Grappler a/t
Pro Comp 2.5" level lift
MBRP 4" turbo back straight no muffler/cat
Black billet aluminium ford grille and tailgate emblems
Sounds wicked, hauls a$$, turns heads, love it.