With white smoke my guess would be oil from somewhere, and since you say its from the exhaust pipe I would go with either Turbos (were they new or refurb?) or maybe oil is getting blown past the PCVs and into the intake track and after getting burned up through the combustion chamber gets pushed out the exhaust as white smoke. I would first pull your balance tube at the back of your upper plenuem and use a light to see if there is much oil there in your intake.