We have filter screens we sell for our injection (TWM). The weber type with the 2 screens and a layer of foam were to restrictive. When we ran them on a dyno there was a 80 to 100 hp drop with the weber screens. The ones shown in the attachment are 2 layers of screen that keep out most things we come across while driving. I don't drive my car in dusty environments anyway, and they are easy to clean. The hp loss on a dyno is almost nothing. On the TWM airhorns we have machined a 40 thousanths deep, 1/8 inch wide groove in the mounting flange of the airhorn. We put a piece of round #14 304 stainless mesh in the groove and bolt the airhorn on. We can put another round piece of mesh inside the airhorn on top of the secured mesh. This filters and does not detract from the looks of the airhorn. More ideas, hope this helps. Al