Plug in wing-root vent?

[Red Air Rambo]

Did not have a chance to look at the 78 model, but on page 383 of the service manual, if i'm correct (not an A & P) the air scoops on the wing go to the aft Pressurization through the ceiling of the cockpit, while the front pressurization goes thru the left inlet and heat exchanger. All P models show just one hose off the scoop for the aft pressurization. Can't find where that second hose goes yet. Any other mods to the aircraft that you know of that require air?