Okay, cost effectiveness isn't a good trade off, meaning the gain from the K&N FIPK doesn't equate the +$200 cost.
I have used a full K&N intake on previous vehicles and the gain was considerable.
I would spend the money on a freeflow muffler and a panel K&N filter.
Save some in the end. That's what I did and if I can keep my foot out of the pedel, because the gained HP is fun, I'll get a better than stock mileage return...
The only benefit is not having to replace the filter element.
The people claiming the "dirt" are measuring dirt so small it's not going to affect anything. But if you're worried about the dirt, that's what the oil's for. Go over to Syn oil and change it on a regular basis and use a good filter and the "dirt" is taken care of.
Now if you don't care about the cost of the FPIK, go for it, horsepower is always good.
Hope that helped.