well it is nice to be able to use a really large dia tube etc, but ONLY if it doesn't need a 'kink' somewhere, or have to make a 90 deg bend etc. If it does, any advantage is most likely lost.
The modified fiero airbox that Darth used on a 3.4 might not be as undersized as you think, ESPECIALLY if it means the tube to the TB will be quite straight (will it? I don't know).
And for air VOLUME issue, you might consider the fact that the 3.4 probably flows as much air volume as a 3800 - it redlines (stock) at 7000. I am guessing the 3800 redline around 6K somewhere? You can think about how much air an engine will flow at redline in terms of its displacement times the rpm. So for a simple volumetric comparison, the 3.4 x 7000 rpm relates to 23800 "UNITS" of airflow. The 3.8 x 6000 rpm would be 22800 on the same scale; so they are in the same ball park. And if it avoids ANY kind of elbow or kink, that is a
very significant bonus.
Just a thought; for what it is worth.
If you don't like that, I have a hipo 5.0 liter mustang airbox that has a 3.5" dia outlet to the TB. Again, compare that volumetrically to the 3800 and maybe you are making life a bit difficult for yourself?.........

It is another 32% larger than the 3800.... Pic attached.