90 Trooper Air Cleaner

Hoping to find somebody to answer some air intake questions.
1. Why does the (4-cyl) engine need the approx 3 inch pipe running across the radiator and up behind the battery to get air?
It seems like a long way to go just to get cool air.
2. What is the function of the pie-shaped section inside of the air cleaner assembly that gets air through an open aprox 3/4" hole?
3. Any reasons not to install a K&N style filter and replace of the whole assembly? The stock unit does an excellent job of keeping the filter dry, so assume that we have the new filter in a dry place.
My '90 Trooper was a project car I got last November. When I got it there was no bumper or grill and one fender was mangled. The windshield was cracked and some lights were broken or missing. It had been declared a total loss by the insurance company. I later found out it had a cracked head. It has 130K miles and is still worth more than I have in it. I had a lot of fun fixing it up and I'm going to keep it for my daily driver.
Ken in Reno
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