Temperature and pressure are related, as temperature goes up, then the pressure goes up given the same volume. That is just laws of physics. The case of the OP can be caused when there is not enough air or dirty stove. However many people on this forum do like Selkirk DT and I recommend it too. Don't forget, that vacuum cleanout is the coolest feature! Anyway to make a pellet stove work better and easier to keep clean is always a good thing!