I removed the air duct as well, but I am thinking about reinstalling it after some trimming. You can buy a replacement for $36-$56. I would rather not have such large "unfiltered" openings into the engine compartment on both sides of the FMIC.
I also replaced three of the sheet metal nuts holding the lower pan on with plastic rivets. I was very uncomfortable with the FMIC sitting on the hardened sheet metal nuts.