So as I removed hardware from the TwistStang I got a good look at the air filter. I then removed it from the rubber case and saw this.
As it has been coming apart wonder where it has all gone?
Guess I need to change them more often???
Well, that's pretty dirty. I would clean mine in either SIG Airplane Cleaner (the stinky solvent kind, not the water-based product) or IPA about once a year. Put it in an old 35 mm film can, pour in about 1/4" of cleaning fluid, and shake the heck out of it. That will get it clean.
I used those pretty religiously for quite a while. The only time I ever had a problem was (predictably) at the 1997 NATs. The element broke away from the plastic ring for about half the circumference, on a qualifying flight, and the engine went slightly lean. Fortunately it was near the peak anyway, so it had only a minor effect.
The only issue is fitting in the cowl. When I went to the RO-Jett, the "trumpet" intake didn't give me enough clearance, so I switched to the panty-hose and o-ring. It probably doesn't filter as well, but it takes up almost no space. Either style does a decent job of acting like a diffuser, or so it would seem.
You can use any of these to make slight venturi tweaks. The "coarse" gray filter, or about two layers of pantyhose, is about like subtracting about a half AWG # drill size, and the "fine" tan/amber filter like you show, or about 4 layers of pantyhose, is about a full AWG # drill size.
I use the Bru-line filter on the Skyray, as it keeps the dirt from the inevitable crashes out of the engine. It works well for that even without the element - the rubber part bends over the intake when it enters the ground and covers it up. Other than that I would be surprised if it did much unless you are taking off in a very gritty/dusty area.
Brett