If I had smoke in the distribution air, there are two things I would check.
First, the outside air intake. It's pyramid-shaped with four louvers that draw in fresh air for both combustion and distribution. If you're running a "T" (as shown in the installation manual), I would consider capping the bottom. It's very easy under certain conditions for smoke coming from the bottom of the open "T" to be drawn into the stove's intake.
Second, when you have the opportunity, remove the round pipe from the intake/exhaust fitting (outside the house) and look into the exhaust portion of the fitting coming from the stove. The exhaust is a square passage and it is coaxially positioned inside of the intake air passage. If the walls of the exhaust passage have corroded, there is a direct connection between exhaust and intake gasses. You can generally patch the corrosion with some aluminum flashing or a small sheet of stainless. Just make sure to inspect it at least a couple times a year. Hi-temp RTV makes a good adhesive with which to attach the new flashing.
I've had to do this with my DVC-500, as well as fabricate an aluminum liner for the hopper which was rusting out from wet coal.