Do an internet search about the V6 and K&N performance results.
I found les performance as the design restricts air flow due to the rubber disc in the center.
Try running with no filter for a short test drive and see if you notice any difference. Then try a clean paper filter.
The "open" K&N filters is where the gains are made but wont fit the 4Runners in stock configurations, assuming you used the "drop in" filter replacement.
The more frequent attention is due to the small filter and location of the intake my paper elements have become plugged within months of summer driving in the mountains.
There are many posts and some in Brians sticky about performance improvements.
Keep in mind the 4Runner is a "Fat Car" and is known to be sluggish and a gas hog.
I am looking to buy a VW to drive for my summer vacation. Soley because of the oil companies GREED!