there was some studies that showed high flow air filters also let more particulates in. There was a direct relation to the amount of particulates to the amount of air flow. The stock paper filter was the best at filtering, but also restricted the most air. I decided engine longevity was more important to me so I stayed with the stock filter.

LOL, I've already spent A YEAR in this forum But mostly was in the Ralliart section till last week I knew there are tons of things for X I need to learn, gotta study hard

I just put a K&N in my SE, not bad in my opinion, reputable company. Used it in my ralliart and you can hear the boost and BOV a lot better, you can get it at pep boys, autozone, etc for like 55 bucks

I'll put my .02 cents here. Cosworth Panel Air filter.

Does not affect the air-fuel ratio and needs no additional tuning if your looking to keep it stock for the time being. Great power gains and at $43 a great buy. Read up on the this filter at this board and many others. consult with tuners and many will agree this filter is top notch.

I use this my gsr. Can hear boost and bov a lot more over stock.

Cosworth filter is the best. Its non-oiled and is made of similar material to the Ralliart filter at 1/3 the price. and its also stock appearing from the outside if that matters to you.

That is something I liked with my Ralliart filter... 100% stock appearing. So +1 there. I have read good things about Cosworth, just haven't seen one in person yet.

Okay, I am planning to get either Ralliart or Cosworth for my next move lol. So here comes the question: for the stock X SE, should I drop the filter in BEFORE the custom tune or AFTER? What's the difference?

sorry if i am missing something, been a few days since i have read this thread.

if you have a cobb AP (which i strongly recommend if you are new to the tuning world), then you flash the new map, and then install the drop in. The order really doesn't matter as long as you don't drive around before flashing.

If you are taking it to a custom tuner, then just have him throw it in there as he is doing the tune.

both of those filters should be fine without an immediate tune, but I recommend a tune (wether the AP or a tuner) as a first mod of these cars.

from what I've read the ralliart is the best, but not the best for the money.. cosworth is the way to go, the oiled filters kn/hks are prone to people not applying the correct amount of oil when they clean/reoil them which messes with the maf.. So, cosworth use it, toss it when dirty buy another.