No OAK. I didn't know that it helped with negative pressure? I was ok with using warm air for combustion and I didn't really like idea of drilling hole through wall.
I think I will try to add more pipe, if that doesn't work, I will explore the OAK. Thanks guys.
If you're willing to add more pipe, that seems to help most folks. To replicate the effect of oak on draft open an outside door near the stove. That will defeat any negative pressure inside the house.