The stock v-6 filter should work fine as it was installed on V-8 engines:
Early 1990's Pontiac Firebird with the 5.0 and 5.7 litre engines the flow through the can just needs some assistance.
If you would like to keep the air filter in the engine bay, while keeping a cold air line outside in 3" use a cavalier filter housing with some mods: more in
https://www.fiero.nl/forum/Forum2/HTML/096287.htmlAnd use a carb hat similar to what Jake_Dragon sugested.
Ditch the air intake muffler
I cut out the bracket that holds the filter can, and built a 120 degree elbow out of two tight 90 degree abs elbows. This elbow is more of a offset 95 degree elbow that is shifted towards the front of the car at the bottom. I also used a rubber gasket instead of the original cork
You could leave the stock bottom elbow in, and just remove the cross and glue the air can on, or use Rodney's cross
Some air filter oil is visible from on the filter gasket in this next picture.
I removed the bottom cross and made a insert out of 3” abs that can be seen in the next photo
if you do this the fuel evap can does not need to be moved, as you can adjust where the hose connects, however since i have a stock 2.8, I used the stock snorkel requiring the fuel vapour can to be moved.
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1988 Fiero GT