UPDATE: The augmenter tubes are part of the Fletcher down draft cooling modification. These large openings increase airflow through the engine compartment, allowing more air to pass and improving cooling. This was an upgrade from the original cooling design. Bonus is that it makes the airplane sound awesome, but it does not add thrust, this I am sure of. lol.
I am definitely not an expert, but I absolutely love flying my Navion. So, I thought I would share a bit of what I know about the airplane and what its like to fly one of these awesome and often overlooked aircraft. If you just want to see some flying and do not want to listen to me blabbering on, just skip ahead to about 17 min in.