BTW, I test things I wonder about. And I wondered about how much junk a muffler blows down the muffler pressure line. So I stuck that filter in that line. I wanted a disconnect point and was cutting the line anyway, so I decided to do the test while I was at it.

If you look closely, you'll see that the filter on that pressure line is backwards. Yeah, some filters work better one direction and not so good in the other. The screen is usually at one end of the filter body. Sometimes the inside of the body is larger than the flow-through diameter of the fittings on the end. The idea is to provide room for the junk that's being trapped.

BTW, years ago, modelers discovered that the larger cavity a filter provides can cure engine run problems. But that's another story.

Anyway, when I first placed the filter ane when replacing after checks, I paid great attention to insure that the cavity was toward the muffler. After later inspections turned up less and less junk, I quit paying attention to the filter orientation. So the experienced modelers with sharp eyes and good observation skills will notice that I've committed a grievous sin, and put the freekin' filter in the line "backwards". Guess I need to either go take another picture or doctor that one.