It's been some 7,500 miles and a few years since I pulled and cleaned the ITG filter and, in preparation for an up-coming HPDE, I decided to do it again. To my surprise, it looked rather pathetic. Small pieces of the exterior foam were lying in the housing. The last time I cleaned it, I used the ITG approved NO-TOIL brand cleaner and oil and I started the procedure again. As soon as the filter hit the warm water, I could tell that this would not end well. The foam separated from the wire cylinder and the seam split. I'm certainly glad I decided to service the ITG because, had it continued to deteriorate, small pieces of foam could've been ingested into the throttle body. Since the AMSOIL filter is NLA, I've ordered a K&N RU-1330. If you haven't checked your ITG lately, I heartily suggest you do so.

 

I had a similar experience with the alta foam filter. I ended up going with the K&N RU-1520. I think the foam filters offer better filtration, but I don't like having to worry about them falling apart.

 

Same thing happened to the ALTA foam filter in our 2005 R53. Even using the prescribed cleaner and oil, they just seem to deteriorate. Anyone got a clue?

 

Same experience with the Pipercross filter here.

 

I was contemplating foam, and specifically ITG,
but keep reading stories of degradation and crumbling foam,
so will likely avoid.

I like the idea that they may flow better, but short lifespan is a major compromise given the cost.

I'm bummed out that Amsoil discontinued their air filters --- previous owner of my car had fitted a 3570 it seemed fine but the color was faded looking,
I replaced with a new one so it should last a good while, but in the meantime I've looked into what I want to go with next.

Using the Amsoil chart as a baseline for fitment...



...but I'm sure there's a little wiggle room there?

AFE offers a "build your own" option:

https://afepower.com/build-your-own-filter



You can also choose media type,
oiled cotton gauze or dry synthetic.

https://afepower.com/air-filter-media

Here's an off-the-shelf filter that is close to spec,
top is 1/2" smaller than Amsoil.
(dry synthetic version)
https://afepower.com/afe-power-21-35...y-s-air-filter

:

This wet cotton one looks like a good fit
and I like that it has the inverted cone top.

https://afepower.com/afe-power-tf-90...-5r-air-filter

:

Green Filters seem to be very well-made in both construction and materials,
a couple of videos doing comparisons with K&N showed the Green to appear "better built",
could not find a suitable universal fitment for JCW airbox tho.

https://greenfilter.com/universal-cylinder

:

Also while looking,
came across interesting test results,
like this:



:

And this one from
Autosalon Magazine, issue 51, Jan 2007

 

Also look at the transition at the neck, best would be a filter with a good velocity stack. I bought this one on Aliexpress and didnt think much of it, but it a very smooth transition in the neck. Cannot be used in the JCW airbox, but I just wanted to point out a much overlooked feature.

https://nl.aliexpress.com/item/33046865396.html

This is how the ITG (Vecchio Engineering, looks identical) and the Pipercross look

 

My ITG did not have the black molded ring at the base.