I agree that brand doesn't really matter in this discussion. It really matter of catted vs. Non-catted. When one has cats installed, its like looking through ray Charles's glasses..... Everything is hidden.
So to make a split as to if the issue is catless dp or the input to the catless dp, you had the dp's on both sides right? Only one was smoking right? If yes to both statements, then the input to the down pipe is the issue and then you have to problem solve that.
Looking at the input to the dp, make a split, is it localized oil leaking or excessive oil leaking due to blow by in the engine? Since you don't see smoke coming out of the drivers side as well, it can't be blow by sucked through the pcv system through the intake. It could be a localized piston on the back bank, but I think that would create a lot if blow by that would be ingested by the intake and the other banks would burn the oil.
So my problem solving of the facts as I know it has lead me to think that your issue is after the engine and before the inlet of the down pipe. What's between there?
Put the dp's back on and take it to the dealer. Show them the smoke and then let them problem solve from there.
John