You do NOT want a tall, lazy flame! The flame should be just at the top of the burn pot, or a little above, on most stoves. Covering the air intake that results in a tall, lazy, looping type of flame is NOT a "great flame". If the stove continues to burn after you hold your hand over the air intake, there would seem to be an air leak somewhere. IMO, it should start to die while doing that. As for upgrading to the 4" pipe, it certainly wouldn't hurt....you right on the borderline of having to put it in due to the altitude.....normally above 2500' requires 4".